Multiple plate clutch

ABSTRACT

In a multiple plate clutch having a main spring which is provided between a clutch center fixed in an axial direction and a pressure plate displaceable in the axial direction and presses plural clutch plates in a clutch engagement direction, and a lifter plate for lifting the pressure plate in a clutch release direction, a sub spring for urging the pressure plate in the clutch engagement direction through the lifter plate is provided between the clutch center and the lifter plate, and the lifter plate is lifted by a predetermined amount or more to cut off the urging force of the sub spring to the pressure plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application of U.S. patent application Ser. No.14/768,358, filed on Aug. 17, 2015, which is a 371 of InternationalApplication No. PCT/JP2014/059155, filed on Mar. 28, 2014, which claimsthe benefit of priority from the prior Japanese Patent Application No.2013-074735, filed on Mar. 29, 2013, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a multiple plate clutch.

BACKGROUND ART

The present invention relates to a clutch of an automatic transmissionvehicle (AT vehicle). AT vehicles have a problem that shock under gearshift should be reduced as much as possible because gear shift isautomatically performed. The shift shock can be recognized as “theamplitude of acceleration which a driver senses bodily”. The driver'sbodily-sensed acceleration amplitude occurs due to variation of acountershaft torque under gear shift (the driving force of a rear wheelas a driving wheel is also in one-to-one relation with the countershafttorque, and variation of the driving force of the rear wheel can beregarded as being the same as the variation of the countershaft torque).

The principle of occurrence of the shift shock will be describedhereunder.

A condition that shift-up from 1-speed to 2-speed is performed in aconventional motorcycle as disclosed in Patent Document 1 is assumed.FIG. 18 shows an example of ratios of driving system parts. The initialvalue of the number of rotations of a clutch outer is set to 1500 rpm.The ratios and the initial value of the number of rotations of theclutch outer are expediencies. Particularly, various values may be takenas the initial value of the number of rotations according to thedriver's driving manner.

FIG. 16 shows the transition of the countershaft torque under up-shift,and FIG. 17 shows the transition of the number of rotations of thedriving system parts under up-shift. The difference in number ofrotations between the clutch outer and the clutch center is defined as“clutch rotation number difference”.

First, attention is paid to the countershaft torque and the transmissionof the rotation number.

(1) Before an up-shift operation, the number of rotations of the clutchouter is set to 150 rpm in accordance with Ne-Th (Engine rotationnumber-Throttle opening) at that time, and a fixed countershaft torqueoccurs. With respect to the number of rotations of the driving systemparts, the number of rotations of the clutch center would be equal to1500 rpm if no slipping is assumed because the clutch is set under aclutch engagement state. The clutch center rotates integrally with amain shaft. The countershaft is driven by the main shaft, and the numberof rotations of the countershaft is equal to 50 rpm in accordance withthe gear ratio 3 of 1-speed. The rear wheel is driven by thecountershaft, and the number of rotations of the rear wheel is equal to20 rpm in accordance with the final reduction ratio of 2.5.

(2) When gear shift is started and the clutch is released, the drivingforce is not applied from the engine to the countershaft, so that thecountershaft torque is temporarily equal to zero. With respect to thenumber of rotations of the driving system part, the clutch outer wouldbe kept to 1500 rpm if it is simply assumed that Ne is kept constantbecause a mechanical throttle is used in the embodiment. However, underthe state of (2), the clutch is released, so that the main shaft, thecountershaft and the rear wheel are not driven by the engine (therotation of the clutch outer). Under the clutch OFF state, the rearwheel side is set to drive the transmission side. Here, when it isassumed that the number of rotations of the rear wheel is fixed to 20rpm while the vehicle speed is kept constant, the number of rotations ofthe countershaft is equal to 50 rpm in accordance with the finalreduction ratio of 2.5, and the number of rotations of the main shaft(clutch center) is equal to 1500 rpm in accordance with the decelerationration 3 of 1-speed. As a result, even under the clutch OFF state, thedifference in the clutch rotation number is equal to zero at the timepoint at which the gear position is set to 1-speed.

(3) Subsequently, the gear position shifts to 2-speed while the clutchis kept to be released. Since the clutch is kept to be released, thecountershaft torque is kept to be zero. With respect to the rotationnumber of the driving system part, the clutch outer is kept to 1500 rpm.Even under the state of (3), the rear wheel side is set to drive thetransmission side. Therefore, when the number of rotations of the rearwheel is equal to 20 rpm, the rotation number of the countershaft isequal to 50 rpm in accordance with the final reduction ratio of 2.5.Here, when the gear position shifts to 2-speed, the number of rotationsof the main shaft (clutch center) is equal to 75 rpm in accordance withthe deceleration ratio 1.5 of 2-speed. That is, the number of rotationsof the clutch center decreases to be lower than that under state of (2)under which the gear position is set to 1-speed. As a result, thereoccurs a difference in clutch rotation number of (clutch outer 1500rpm)−(clutch center 75 rpm)=(clutch rotation number difference 75 rpm)at the time point when the gear position shifts to 2-speed under theclutch OFF state.

(4) When the clutch is engaged, the clutch rotation number difference isabsorbed by the clutch. The multiple plate clutch is configured so thattwo rotators having different numbers of rotations are connected to eachother in accordance with the capacity of the clutch while slipping so asto be matched with the same rotation number. When the clutch capacity islarge, the difference in clutch rotation number per unit time can begreatly reduced. At this time, a shaft at which the number of rotationsis increased due to the clutch engagement is instantaneouslyaccelerated, and thus the torque of the shaft concerned greatly rises upwhile the clutch rotation number difference is absorbed. Conversely,when the clutch capacity is small, the clutch is liable to slip and thusthe decrease of the difference in clutch rotation number per unit timelessens. At this time, the shaft at which the number of rotationsincreases due to the clutch engagement is gradually accelerated, so thatthe rising degree of the torque of the shaft concerned is low. The timefor which the difference in rotation number is absorbed is long.

That is, the countershaft torque during the absorption of the rotationnumber difference is determined in accordance with the clutch capacity.When the clutch capacity is large, the countershaft torque is large, andwhen the clutch capacity is small, the countershaft torque is small.

With respect to the rotation number of the driving system part, when theclutch center is assumed to be kept at 1500 rpm, the rotation numbers ofthe main shaft, the countershaft and the rear wheel are also switched tobe driven by the engine side (clutch center). As a result, the clutchcenter whose rotation number is equal to 75 rpm at the time point of (3)is accelerated to 1500 rpm in the time corresponding to the clutchcapacity.

(5) When the gear shift is finished after the difference in clutchrotation number is absorbed, the gear is shifted up by one step from thejust-before gear state, and thus the countershaft torque is lower thanthat at the time point of (1). With respect to the rotation number ofthe driving system part, when the rotation number of the clutch outer iskept at 1500 rpm, the rotation number of the clutch center is equal to1500 rpm because the difference in clutch rotation number is absorbed.Since the clutch center rotates integrally with the main shaft, therotation number of the countershaft is equal to 1000 rpm in accordancewith the gear ratio 1.5 of 2-speed, and the rotation number of the rearwheel is equal to 40 rpm in accordance with the final reduction ratio of2.5.

Here, paying attention to the rotation number of the rear wheel between(3) and (5), in the process of (4), the rotation number of the rearwheel increases from 20 rpm to 40 rpm. That is, acceleration occurs.When this acceleration is rapid, the counter shaft torque quicklyincreases, which causes shift shock. Next, time charts will be viewedwhile attention is paid to acceleration amplitude of FIG. 16. (1) Thereis no acceleration amplitude before shift-up because the countershafttorque is constant. (2), (3) when shift change is started and the clutchis released, the countershaft torque is equal to zero, so that thebodily-sensed acceleration swings so as to decrease. (4) thebodily-sensed acceleration during absorption of the difference inrotation number difference swings so as to follow the value whichcorresponds to the countershaft torque corresponding to the clutchcapacity. (5) Thereafter, the bodily-sensed acceleration swings so as tofollow the value corresponding to the countershaft torque after theshift-up is completed.

From the viewpoint of suppressing the shift shock, it is important thatthe clutch capacity during absorption of the difference in clutchrotation number is variable. The reason for this is as follows. Thecountershaft torque before and after gear shift is changed to be high orlow in accordance with the driving state, but the countershaft torqueduring absorption of the difference in clutch rotation number isdetermined in accordance with the clutch capacity. Therefore, when theclutch capacity is fixed, (4) during absorption of the difference inrotation number and (5) the clutch engagement is completed, theacceleration amplitude may be large depending on the driving state.

When the clutch capacity is variable, in order to suppress the shiftshock, the clutch capacity during absorption of the difference inrotation number may be set between the countershaft torques before andafter the gear shift, whereby the countershaft torque during absorptionof the difference in rotation number can be adapted to the countershafttorques before and after gear shift, and the acceleration amplitude canbe suppressed as much as possible. Conversely, as the clutch capacity isfarther away from the band of the countershaft torques before and aftergear shift, the acceleration amplitude is more intense, and thus shiftshock is more easily sensed.

The multiple plate clutch disclosed in the Patent Document 1 has amechanism that has a clutch spring for urging a pressure plate in aclutch engagement direction and a release spring for urging the pressureplate in a clutch release direction in accordance with a lift mount of alifter plate which is displaceable relatively to the pressure plate, andin which the clutch capacity is reduced in accordance with the liftamount of the lifter plate. According to the construction of the PatentDocument 1, by properly controlling the lift amount of the lifter platewhen the difference in rotation between the countershaft and the engineside is absorbed at the start of the clutch engagement under gear shift,the clutch capacity can be adjusted, and the shift shock can be reduced.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: JP-2005-249083

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

However, the conventional multiple plate clutch described above is ofsuch a type that the clutch capacity is adjusted steplessly. Therefore,in order to match the clutch capacity with a targeted clutch capacity,high-precision parts for a control system and a high-precision controlmethod are required, and thus there is a problem that the structure iscomplicated.

The present invention has been implemented in view of the foregoingsituation, and has an object to provide a simple structure capable ofimplementing a multiple plate clutch that can reduce shift shock byvarying a clutch capacity.

Means of Solving the Problem

This specification contains the whole content of Japanese PatentApplication No. 2013-074735 filed on Mar. 29, 2013.

In order to solve the above problem, according to the present invention,a multiple plate clutch having a main spring (95) that is providedbetween a clutch center (92) fixed in an axial direction and a pressureplate (93) displaceable in the axial direction and presses a pluralityof clutch plates (94) in a clutch engagement direction, and a lifterplate (96) for lifting the pressure plate (93) in a clutch releasedirection, is characterized in that a sub spring (97) for urging thepressure plate (93) in a clutch engagement direction through the lifterplate (96) is provided between the clutch center (92) and the lifterplate (96), and the lifter plate (96) is lifted by a predeterminedamount (L1) or more to thereby cut off the urging force of the subspring (97) to the pressure plate (93).

According to the present invention, the lifter plate for lifting thepressure plate in the clutch release direction is lifted by thepredetermined amount or more, whereby the urging force of the sub springto the pressure plate is cut off. Therefore, the clutch engaging loadcan be secured by the main spring and the sub spring which act in theclutch engagement direction, and by lifting the lifter plate under gearshift, the urging force of the sub spring to the pressure plate is cutoff, and the clutch engaging load can be produced by only the mainspring. Accordingly, the clutch capacity can be set at plural stages ofthe maximum capacity under the clutch engagement state and theintermediate capacity under the state when the lifter plate is lifted,and the multiple plate clutch which can reduce shift shock by changingthe clutch capacity can be implemented with a simple structure.

When the clutch of the present invention is adopted, for example, as aclutch for an AT vehicle, the intermediate capacity of the clutch can beeasily matched with a set value even in the case of a system part forcontrolling the intermediate capacity of the clutch or a relativelysimple control method.

The present invention is characterized in that the pressure plate (93)is provided with a release boss (99) extending to the lifter plate (96)side and a stopper plate (105) fixed to an end portion of the releaseboss (99), the lifter plate (96) is provided with a hole portion (96 b)having a smaller diameter than the stopper plate (105), and the releaseboss (99) is inserted in the hole portion (96 b).

According to the present invention, the lifter plate is provided withthe small-diameter hole portion which is smaller in diameter than thestopper plate, and the release boss is inserted in this hole portion.Therefore, the construction that the urging force of the sub spring tothe pressure plate is cut off while suppressing the number of parts atmaximum can be implemented.

Furthermore, the present invention is characterized in that the multipleplate clutch has a clutch outer (91) disposed at an outside of theclutch center (92) in a radial direction, the plurality of clutch plates(94) contain outer friction plates (94 a) provided to the clutch outer(91) and inner friction plates (94 b) provided to the clutch center(92), the outer friction plates (94 a) and the inner friction plates (94b) being alternately arranged between the clutch center (92) and thepressure plate (93), and the main spring (95) is disposed at theopposite side to the lifter plate (96) in the axial direction andbetween a hub portion (92 a) of the clutch center (92) and the pressureplate (93).

According to the present invention, the main spring is disposed at theopposite side to the lifter plate in the axial direction and between thehub portion of the clutch center and the pressure plate, and the mainspring and the sub spring can be disposed at both the sides of theclutch center. Therefore, the number of pats serving as the seats forthe main spring and the sub spring can be reduced, and the main springand the sub spring can be compactly disposed.

The present invention is characterized in that the sub spring (97) isprovided as a ring-shaped disc spring and disposed at an outside of therelease boss (99) of the pressure plate (93) in the radial direction.

According to the present invention, the sub spring can be provided witha small number of parts, the degree of freedom for design of the subspring can be secured by using the space at the outside in the radialdirection of the release boss, and the load of the sub spring can beeasily secured.

Furthermore, the present invention is characterized in that a stepportion (99 c) which is larger in diameter than the hole portion (96 b)of the lifter plate (96) is provided at the pressure plate (93) side ofthe release boss (99) of the pressure plate (93), and when the lifterplate (96) is lifted by only a second predetermined amount (L2), thelifter plate (96) comes into contact with the step portion (99 c), anddirectly moves the pressure plate (93).

According to the present invention, when the lifter plate is lifted byonly the second predetermined amount, the lifter plate comes intocontact with the step portion of the release boss, and directly movesthe pressure plate, so that the clutch can be released with a simpleconstruction while providing the construction of cutting off the urgingforce of the sub spring.

Furthermore, according to the present invention, a multiple plate clutchhaving a main spring (95, 295, 395) that is provided between a clutchcenter (92, 292, 392) fixed in an axial direction and a pressure plate(93, 293, 393) displaceable in the axial direction and presses aplurality of clutch plates (94) in a clutch engagement direction, and alifter plate (96, 296, 396) for lifting the pressure plate (93, 293,393) in a clutch release direction through the sub pressure plate (96,210, 310) is characterized in that a sub pressure plate (96, 210, 310)which is separate from and displaceable relatively to the pressure plate(93, 293, 393), a sub spring (97, 297, 397) for pressing the pressureplate (93, 293, 393) in a clutch engagement direction is provided, andwhen the lifter plate (96, 296, 396) is lifted by a predetermined amount(L1), the lifter plate separates the sub pressure plate (96, 210, 310)from the pressure plate (93, 293, 393), thereby cutting off a sub springload transmission passage (S) to the pressure plate (93, 293, 393).

According to the present invention, when the lifter plate is lifted bythe predetermined amount, the lifter plate separates the sub pressureplate from the pressure plate, whereby the sub spring load transmissionpassage to the pressure plate is cut off. Therefore, the clutch engagingload can be secured by the main spring and the sub spring which act inthe clutch engagement direction, and also when the lifter plate islifted under gear shift, the sub spring load transmission passage to thepressure plate can be cut off, and the clutch engaging load can beproduced by only the main spring. Accordingly, the clutch capacity canbe set at multiple stages of the maximum capacity under the clutchengagement state and the intermediate capacity under the state that thelifter plate is lifted, so that a multiple plate clutch which can reducethe shift shock by changing the clutch capacity can be implemented witha simple construction.

For example, when the clutch of the present invention is adopted, forexample, as a clutch for an AT vehicle, the intermediate capacity of theclutch can be easily matched with a set value even in the case of arelatively simple system part for controlling the intermediates capacityof the clutch or control method.

Furthermore, the present invention is characterized in that the subspring (297, 397) and the sub pressure plate (210, 310) are disposed atthe opposite side to the lifter plate (296, 396) through the pressureplate (293, 393), the pressure plate (293, 393) is provided with a holeportion (293 e, 393 e), the lifter plate (296, 396) is provided with arelease boss (271) to be inserted in the hole portion (293 e, 393 e),and when the lifter plate (296, 396) is lifted by the predeterminedamount (L1) or more, the release boss (271) comes into contact with thesub pressure plate (210, 310), whereby the sub pressure plate (210, 310)is separated from the pressure plate (293, 393).

According to the present invention, when the lifter plate is lifted bythe predetermined amount or more, the release boss comes into contactwith the sub pressure plate, so that the sub pressure plate separatesfrom the pressure plate. Therefore, even in the construction that thesub spring is disposed at the opposite side to the lifter plate, themechanism of cutting off the sub spring load transmission passage can beprovided with a simple construction.

Furthermore, the present invention is characterized in that a flangeportion (270) which is larger in diameter than the hole portion (293 e,393 e) of the pressure plate (293, 393) is provided to an intermediateportion in the axial direction of the release boss (271) of the lifterplate (296, 396), and when the lifter plate (296, 396) is lifted by onlya second predetermined amount (L2), the flange portion (270) comes intocontact with the pressure plate (293, 393) and directly moves thepressure plate (293, 393).

According to the present invention, when the lifter plate is lifted byonly the second predetermined amount, the flange portion comes intocontact with the pressure plate, and directly moves the pressure plate.Therefore, even in the construction that the sub spring loadtransmission passage is provided, the clutch can be released with asimple construction.

Still furthermore, the present invention is characterized in that themultiple plate clutch has a clutch outer (91) disposed at an outside ofthe clutch center (292) in a radial direction, wherein the plurality ofclutch plates (94) contain outer friction plates (94 a) provided to theclutch outer (91) and inner friction plates (94 b) provided to theclutch center, the outer friction plates and the inner friction platesbeing alternately arranged between the clutch center (292) and thepressure plate (293), the sub spring (297) and the sub pressure plate(210) are disposed between a hub portion (292 a) of the clutch center(292) and the pressure plate (293), and the main spring (295) isdisposed between hub portion (292 a) of the clutch center (292) and thepressure plate (293) to be nearer to the clutch outer (91) side than thesub spring (297).

According to the present invention, the sub spring and the sub pressureplate are disposed between the hub portion of the clutch center and thepressure plate, and the main spring is disposed between the hub portionof the clutch center and the pressure plate to be nearer to the clutchouter side than the sub spring, so that the main spring and the subspring can be compactly disposed at the same side.

Still furthermore, the present invention is characterized in that bothof the sub spring (297) and the main spring (295) are provided asring-shaped disc springs, the sub pressure plate (210) is inlaid in thepressure plate (210), a seat portion (210 c) of the sub spring (297) isprovided at an outside thereof in the radial direction, and the pressureplate (293) is provided with a seat portion (212 d) for the main spring(295) at an outside in the radial direction of an inlay hole (212 e) inwhich the sub pressure plate (210) is fitted.

According to the present invention, the sub spring load transmissionpassage and the cut-off mechanism therefor can be provided with simpleconstructions, and further the size of the main spring can be increased,so that the load of the main spring can be easily secured.

Still furthermore, the present invention is characterized in that themultiple plate clutch has a clutch outer (91) disposed at an outside inthe radial direction of the clutch center (392), wherein the pluralityof clutch plates (94) contain outer friction plates (94 a) provided tothe clutch outer (91) and inner friction plates (94 b) provided to theclutch center (392), the outer friction plates and the inner frictionplates being alternately arranged between the clutch center (392) andthe pressure plate (393), a spring holder (315) is provided to a hubportion (392 a) of the clutch center (392), and the sub spring (397),the sub pressure plate (310) and the main spring (395) are disposedbetween the spring holder (315) and the pressure plate (393).

According to the present invention, the sub spring, the sub pressureplate and the main spring are disposed between the spring holder and thepressure plate, so that the main spring and the sub spring can becompactly disposed at the same side.

Still furthermore, the present invention is characterized in that thesub spring (397) and the main spring (395) are provided as coil springsalong the axial direction of the multiple plate clutch so as to be outof phase in a peripheral direction, and the sub pressure plate (310) isprovided with a hole portion or cut-out portion (310 c) in which themain spring (395) passes.

According to the present invention, the clutch capacity can be easilymatched with the set value by the spring characteristic of the coilspring. Since the main spring is passed in the hole portion of the subpressure plate or the cut-out portion, the sub pressure plate can bemoved without affecting the main spring, and both of securing of theclutch load based on the main spring and the cut-off mechanism for anauxiliary load transmission passage can be established.

Still furthermore, according to the present invention, a multiple plateclutch having a main spring (95) that is provided between a clutchcenter (92) fixed in an axial direction and a pressure plate (93)displaceable in the axial direction and presses a plurality of clutchplates (94) in a clutch engagement direction, and a lifter plate (496)which is displaced by a lifter cam (84) to lift the pressure plate (93)in a clutch release direction, is characterized in that a sub lifterplate (410) which is separate from and displaceable relatively to thelifter plate (496) and disposed to be nearer to the lifter cam (84) sidethan the lifter plate (496) is provided, a sub spring (411) for pressingthe pressure plate (93) in a clutch engagement direction through the sublifter plate (410) is provided, and when the sub lifter plate (410) islifted by a predetermined amount, the sub lifter plate (410) isseparated from the pressure plate (93), whereby a sub spring loadtransmission passage (S1) to the pressure plate (93) is cut off.

According to the present invention, the clutch engaging loads of themain spring and the sub spring which press in the clutch engagementdirection can be secured, and the clutch engaging load can be producedby the load excluding the urging force of the sub spring under gearshift. Accordingly, the clutch capacity can be set at multiple stages ofthe maximum capacity under the clutch engagement state and theintermediate capacity under the lifted state of the sub lifter plate.Therefore, a multiple plate clutch which can reduce the shift shock bychanging the clutch capacity can be implemented with a simple structure.

Furthermore, the present invention is characterized in that the pressureplate (93) is provided with a pressure plate side boss (99 b) projectingto the lifter plate (496) side, the lifter plate (496) is provided witha lifter plate side boss (415) which projects to the sub lifter plate(410) side and has a hole (415 a) in which the pressure plate side boss(99 b) penetrates, the sub lifter plate (410) is provided with a hole(422) in which the lifter plate side boss (415) penetrates, an endportion of the pressure plate side boss (99 b) is provided with a fixingmember (105, 106) by which the lifter plate side boss (415) and the sublifter plate (410) are held while the lifter plate side boss and the sublifter plate are assembled, and a load of the sub lifter plate (410) istransmitted to the fixing member (105, 106).

According to the present invention, the load of the sub lifter plate canbe transmitted to the pressure plate through the fixing member, and thesub spring load transmission passage can be formed with a simpleconstruction.

Furthermore, the present invention is characterized in that the lifterplate side boss (415) is set to be larger in length than the thicknessof a peripheral portion of the hole (422) of the sub lifter plate, andwhen the sub lifter plate (410) is lifted by a predetermined amount(G1), the sub lifter plate comes into contact with the lifter plate(496) and displaces integrally with the lifter plate (496).

According to the present invention, the area of the intermediatecapacity of the clutch can be adjusted on the basis of the relationshipof the lifter plate side boss and the thickness of the peripheralportion of the hole of the sub lifter plate, and after the sub lifterplate is lifted by the predetermined amount, the sub lifter plate candirectly lift the lifter plate.

Still furthermore, the present invention is characterized in that eachof the lifter plate (496) and the sub lifter plate (410) has aring-shaped portion (496 a, 420) which is opened at the center side of ashaft (56) of the clutch,

a circular pipe portion (421) which projects from an inner peripheraledge of the ring-shaped portion (420) of the sub lifter plate (410) tothe lifter cam (84) side is integrally provided,

a step portion (423) extending inwards in the radial direction isprovided to the lifter cam (84) side of an inner peripheral surface ofthe circular pipe portion (421), and

the sub spring (411) is disposed between the shaft (56) of the clutchand the circular pipe portion (421), and is in contact with the clutchcenter (92) and the step portion (423) of the circular pipe portion(421).

According to the present invention, the sub spring can be compactlydisposed in the radial direction between the shaft and the circular pipeportion.

Still furthermore, the multiple plate clutch is disposed in a power unitcase (30 c), and a start clutch (24) through which rotation of an engine(21) is input to the multiple plate clutch is disposed within the samewidth in the axial direction as the circular pipe portion (421) in thepower unit case (30 c).

According to the present invention, the start clutch can be disposed byusing the space of the circular pipe portion of the sub lifter plate,and even in the clutch for which the intermediate capacity can be set,the size of the power unit case can be suppressed to a compact size.

Furthermore, the present invention is characterized in that a second subspring (497) for urging the pressure plate (93) in the clutch engagementdirection through the lifter plate (410) is provided between the clutchcenter (92) and the lifter plate (410), and when the lifter plate (410)is lifted by a predetermined amount or more, the urging force of thesecond sub spring (497) to the pressure plate (93) is cut off.

According to the present invention, the clutch engaging load can beobtained by the urging force of the second sub spring, and when theclutch is released, the urging force of the second sub spring is cutoff, whereby the number of stages of the clutch capacity can be furtherincreased.

Still furthermore, according to the present invention, a multiple plateclutch having a main spring (595) that is provided between a clutchcenter (592) fixed in an axial direction and a pressure plate (593)displaceable in the axial direction and presses a plurality of clutchplates (94) in a clutch engagement direction, and a lifter plate (410)which is displaced by a lifter cam (84) to lift the pressure plate (593)in a clutch release direction, is characterized in that a release member(599) is provided between the pressure plate (593) and the lifter plate(410), the release member (599) is provided with a release boss (571)projecting to the lifter plate (410) side, an end portion at the lifterplate (410) side of the release boss (571) is provided with asmall-diameter boss portion (571 b) whose diameter is smaller than thediameter of the release boss (571) at the pressure plate (593) side, thelifter plate (410) is provided with a lifter plate side hole (422) inwhich the small-diameter boss portion (571 b) penetrates, an end portionof the small-diameter boss portion (571 b) is provided with a fixingmember (505, 506) by which the lifter plate is held while the lifterplate (410) is assembled, a sub spring (411) for pressing the pressureplate (593) in the clutch engagement direction through the fixing member(505, 506) is provided between the clutch center (592) and the lifterplate (410), and when the lifter plate (410) is lifted by apredetermined amount, the lifter plate (410) is separated from thefixing member (505, 506), whereby a sub spring load transmission passage(S1) to the pressure plate (593) is cut off.

According to the present invention, under the clutch engagement state,the load of the sub spring for pressing in the clutch engagementdirection is transmitted to the pressure plate through the fixing memberand the release boss, and when the lifter plate is lifted by thepredetermined amount to release the clutch, the sub spring loadtransmission passage of the sub spring to the pressure plate is cut off.Therefore, the clutch engaging loads of the main spring and the subspring which press in the clutch engagement direction can be secured,and the clutch engaging load can be produced by the load excluding theurging force of the sub spring under gear shift. Accordingly, the clutchcapacity can be set at plural stages of the maximum capacity under theclutch engagement state and the intermediate capacity under the statethat the lifter plate is lifted. Therefore, a multiple plate clutchwhich can reduce shift shock by changing the clutch capacity can beimplemented with a simple construction.

Furthermore, the present invention is characterized in that thesmall-diameter boss portion (571 b) of the release member (599) is setto be longer in length than the thickness of a peripheral portion of thelifter plate side hole (422), and when the lifter plate (410) is liftedby a predetermined amount (G1), the lifter plate (410) comes intocontact with and displaces integrally with a step portion (571 c) of therelease boss (571).

According to the present invention, the area of the intermediatecapacity of the clutch can be adjusted on the basis of the relationshipof the small-diameter boss portion and the thickness of the peripheralportion of the lifter plate side hole, and when the lifter plate islifted by the predetermined amount, the lifter plate directly lifts therelease boss.

Still furthermore, the present invention is characterized in that thelifter plate (410) has a ring-shaped portion (420) which is opened atthe center side of a shaft (56) of the clutch, and integrally providedwith a circular pipe portion (421) projecting from an inner peripheraledge of the ring-shaped portion (420) to the lifter cam (84) side, astep portion (423) extending inwards in the radial direction is providedto the lifter cam (84) side of an inner peripheral surface of thecircular pipe portion (421), and the sub spring (411) is disposedbetween the shaft (56) and the circular pipe portion (421) and is incontact with the clutch center (592) and the step portion (423) of thecircular pipe portion (421).

According to the present invention, the sub spring can be compactlydisposed in the radial direction between the shaft and the circular pipeportion.

Furthermore, the present invention is characterized in that the multipleplate clutch is accommodated in the power unit case (30 c), and thestart clutch (24) through which the rotation of the engine (21) is inputto the multiple plate clutch is disposed within the same width in theaxial direction as the circular pipe portion (421) in the power unitcase (30 c).

According to the present invention, the start clutch can be disposed byusing the space of the circular pipe portion of the lifter plate, andeven in the construction that the circular pipe portion is provided, thepower unit case can be miniaturized.

The present invention is characterized in that a sub pressure plate(510) which is separate from and displaceable relatively to the releasemember (599) and the pressure plate (593) is provided, a second subspring (597) for pressing the pressure plate (593) in the clutchengagement direction through the sub pressure plate (510) is provided,and when the lifter plate (410) is lifted by a predetermined amount, thesub pressure plate (510) is separated from the pressure plate (593)through the release member (599), thereby cutting off a second subspring load transmission passage (S2) to the pressure plate (593).

According to the present invention, the clutch engaging load can beobtained by the urging force of the second sub spring, and the number ofstages of the clutch capacity can be further increased by cutting offthe urging force of the second sub spring when the clutch is released.

Effect of the Invention

In the multiple plate clutch of the present invention, the clutchcapacity can be set at multiple stages of the maximum capacity under theclutch engagement state and the intermediate capacity under the statethat the lifter plate is lifted, and the multiple plate clutch which canreduce the shift shock by changing the clutch capacity can beimplemented with a simple construction.

Furthermore, the construction of cutting off the urging force of the subspring to the pressure plate can be implemented while suppressing thenumber of parts at maximum.

Furthermore, the number of parts serving as the seats for the mainspring and the sub spring can be reduced, and the main spring and thesub spring can be compactly disposed.

Furthermore, the sub spring can be provided with a small number ofparts, the degree of freedom for design of the sub spring can be securedby using the space at the outside in the radial direction of the releaseboss, and the load of the sub spring can be easily secured.

Furthermore, the clutch can be released with a simple construction whilethe construction of cutting off the urging force of the sub spring isprovided.

Still furthermore, the clutch engaging load can be secured by the mainspring and the sub spring acting in the clutch engaging direction, thesub spring load transmission passage can be cut off under gear shift,and the clutch engaging load can be produced by only the main spring.

Still furthermore, even in the construction that the sub spring isdisposed at the opposite side to the lifter plate, the cut-off mechanismof the sub spring load transmission passage can be provided with asimple construction.

Furthermore, since the flange portion comes into contact with thepressure plate and directly moves the pressure plate, the clutch can bereleased by a simple construction although the construction is providedwith the sub spring load transmission passage.

Still furthermore, the main spring and the sub spring can be compactlydisposed at the same side.

The sub spring load transmission passage and the cut-off mechanismtherefor can be provided with simple constructions, and the size of themain spring can be increased, so that the load of the main spring can beeasily secured. Furthermore, the sub spring, the sub pressure plate andthe main spring are disposed between the spring holder and the pressureplate, so that the main spring and the sub spring can be compactlydisposed at the same side.

Still furthermore, the clutch capacity can be easily matched with theset value by the spring characteristic of the coil spring. Furthermore,the sub pressure plate can be moved without affecting the main spring,so that both of securement of the clutch load based on the main springand the cut-off mechanism of the auxiliary load transmission passage canbe established.

The sub spring load transmission passage can be formed with a simpleconstruction.

Furthermore, the area of the intermediate capacity of the clutch can beeasily adjusted, and after lifted by the predetermined amount, the sublifter plate can directly lift the lifter plate.

Still furthermore, the sub spring can be compactly disposed in theradial direction.

Still furthermore, even in the construction having the circular pipeportion, the power unit case can be miniaturized.

Still furthermore, the number of stages of the clutch capacity can befurther increased by the second sub spring.

Still furthermore, the area of the intermediate capacity of the clutchcan be easily adjusted, and after lifted by the predetermined amount,the lifter plate can directly lift the release boss.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a left side view showing a motorcycle having a multiple plateclutch according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional plan view of a power unit.

FIG. 3 is a cross-sectional view showing a gear shift mechanism, anactuator mechanism, a clutch mechanism for gear shift, and a clutchoperating mechanism.

FIG. 4 is a cross-sectional view showing the clutch mechanism for gearshift.

FIG. 5 is an example of a diagram showing the clutch capacity of theclutch mechanism for gear shift.

FIG. 6 is a cross-sectional view showing the clutch mechanism for gearshift under an intermediate-capacity state.

FIG. 7 is a cross-sectional view showing the clutch mechanism for gearshift under a small-capacity state.

FIG. 8 is a cross-sectional view showing a clutch mechanism for gearshift according to according to a second embodiment.

FIG. 9 is a plan view of a release member.

FIG. 10 is a cross-sectional view showing the clutch mechanism for gearshift under an intermediate-capacity state.

FIG. 11 is a cross-sectional view showing a clutch mechanism for gearshift according to a third embodiment.

FIG. 12 is a plan view showing a back torque limit member.

FIG. 13 is a plan view showing a spring holder.

FIG. 14 is a plan view showing a sub pressure plate.

FIG. 15 is a cross-sectional view showing the clutch mechanism for gearshift under an intermediate-capacity state.

FIG. 16 is a diagram showing a background art.

FIG. 17 is a diagram showing the background art.

FIG. 18 is a diagram showing the background art.

FIG. 19 is a cross-sectional view showing a gear shift mechanism, anactuator mechanism, a clutch mechanism for gear shift, and a clutchoperating mechanism according to a fourth embodiment.

FIG. 20 is a cross-sectional view showing the clutch mechanism for gearshift.

FIG. 21 is an example of a diagram showing the clutch capacity of theclutch mechanism for gear shift.

FIG. 22 is a cross-sectional view showing the clutch mechanism for gearshift under a first intermediate-capacity state.

FIG. 23 is a cross-sectional view showing the clutch mechanism for gearshift under a second intermediate-capacity state.

FIG. 24 is a cross-sectional view showing the clutch mechanism for gearshift under a released capacity state.

FIG. 25 is a cross-sectional view showing a clutch mechanism for gearshift according to a modification 1.

FIG. 26 is a cross-sectional view showing a peripheral portion of aclutch mechanism for gear shift according to a modification 2.

MODES FOR CARRYING OUT THE INVENTION

Embodiments according to the present invention will be describedhereunder with reference to the drawings.

First Embodiment

FIG. 1 is a left-side view of a motorcycle having a multiple plateclutch according to a first embodiment of the present invention.

The motorcycle 10 has a handle 11 which is turnably pivotally supportedby a head pipe (not shown), a front wheel 12 steered by the handle 11, arear wheel 13 serving as a driving wheel, a seat 14 on which a driversits, a power unit 16 for supplying driving force to the rear wheel 13through a chain 15, a control unit 17 (controller) for controlling thepower unit 16, and a battery 18.

The motorcycle 10 is configured with a vehicle body frame (not shown) asa base body, and the vehicle body frame is covered by a vehicle bodycover 19. The control unit 17 and the battery 18 are disposed below theseat 14 in the vehicle body cover 18. The power unit 16 is providedsubstantially between the front wheel 12 and the rear wheel 13 andslightly in front of the lower side of the seat 14. A pair of right andleft steps 20 for the driver are provided at the lower side of the powerunit 16.

The power unit 16 has an automatic transmission mechanism T (FIG. 2).The automatic transmission mechanism T has a transmission T for whichclutch engagement (connection)/release operation is automated, and inthis automatic transmission mechanism T, switching of the clutchmechanism 51 for gear shift and switching of a shift gear stage (shift)are automatically performed.

Next, the construction of the power unit 16 will be described.

FIG. 2 is a cross-sectional plan view of the power unit 16. In FIG. 2,the right-and-left-direction corresponds to the vehicle width direction,the upward direction corresponds to the forward direction of thevehicle, and the downward direction corresponds to the rearwarddirection of the vehicle.

The power unit 16 has an engine 21 for generating driving force fortraveling, an electric generator 22, a starting clutch 24 provided tothe crankshaft 23 of the engine 21, and an automatic transmissionmechanism T for gear-shifting the driving force of the crankshaft 23output through the starting clutch 24 and outputting the gear-shiftdriving force.

The power unit 16 is constructed by integrally coupling a cylinder head30 a, a cylinder 30 b and a crankcase 30 c. The crankshaft 23 ispivotally supported by plural bearings 31 so as to be freely rotatable.The engine 21 has a piston 33 connected to the crankshaft 23 through aconnection rod 32, an ignition plug 34, and a valve gear mechanism 36for performing intake and exhaust on a combustion chamber 35 byopening/closing a valve (not shown). The valve gear mechanism 36 isdriven through a timing chain 36 a by the crankshaft 23.

The starting clutch 24 performs connection and disconnection between thecrankshaft 23 and a primary gear 37 at the start time and the stop time,and is disposed at the right end portion of the crankshaft 23. Thestarting clutch 24 has a cup-shaped outer case 39 fixed to one end of asleeve 38 which is rotatable relatively to the outer periphery of thecrankshaft 23, the primary gear 37 provided to the sleeve 38, an outerplate fixed to the right end portion of the crankshaft 23, a shoe 42which is secured to the outer peripheral portion of the outer plate 40through a weight 41 so as to face the outside in the radial direction,and a spring 43 for urging the shoe 42 inwards in the radial direction.In the starting clutch 24, when the number of rotations of the engine isequal to a predetermined value or less, the outer case 39 and the shoe42 are separated from each other, and thus the crankshaft 23 and theautomatic transmission T are set to be released from each other (aseparation state under which no driving force is transmitted). When theengine rotation number increases and exceeds a predetermined value, theweight 41 is moved outwards in the radial direction against the spring43 by centrifugal force, whereby the shoe 42 comes into contact with theinner peripheral surface of the outer case 39. Accordingly, the rotationof the crankshaft 23 is transmitted to the primary gear 37 through theouter case 39, and a connection state where the driving force istransmitted is established.

The crankcase 30 c has, at a right side face thereof, a crankcase cover30 d which covers the starting clutch 24 and the clutch mechanism 51 forgear shift (multiple plate clutch). When the crankcase cover 30 d isremoved, the starting clutch 24 and the clutch mechanism 51 for gearshift are exposed to the outside.

The automatic transmission mechanism T has a forward 4-stagetransmission 50, a clutch mechanism 51 for gear shift for switching theconnection between the crankshaft 23 side and the transmission 50, aclutch operating mechanism 52 for operating the clutch mechanism 51 forgear shift, a gear shift mechanism 53 for gear-changing the transmission50, and an actuator mechanism 54 (FIG. 1) for driving the clutchoperating mechanism 52 and the gear shift mechanism 53. The actuatormechanism 54 is controlled by a control unit 17 (FIG. 1).

The automatic transmission mechanism T is connected to a mode switch(not shown) for performing the switching operation between an automatictransmission (AT) mode and a manual transmission (MT) mode, and a shiftselect switch (not shown) with which the driver operates shift-up orshift-down. Under the control of the control unit 17, the automatictransmission mechanism T is configured to control the actuator mechanism54 in accordance with output signals of each sensor, the mode switch andthe shift select switch, whereby the shift stage of the transmission 50can be automatically or semi-automatically switched.

That is, in the automatic transmission mode, the actuator mechanism 54is controlled on the basis of the vehicle speed or the like, and gearshift is automatically performed in the transmission 50. In the manualtransmission (MT) mode, the shift select switch is operated by thedriver, whereby the gear shift is performed.

The transmission 50 gear shifts the rotation supplied from the clutchmechanism 51 for gear shift on the basis of an instruction of thecontrol unit 17 and transmits the gear shift rotation to the rear wheel13. The transmission 50 has a main shaft 56 (main shaft) as an inputshaft, a countershaft 57 disposed in parallel to the main shaft 56,driving gears 58 a, 58 b, 58 c and 58 d provided to the main shaft 56,driven gears 59 a, 59 b, 59 c and 59 d provided to the countershaft 57,a shift fork 60 a engaged with the driving gear 58 a, a shift fork 60 bengaged with the driven gear 59 c, a support shaft 61 for holding theshift forks 60 a, 60 b so that the shift forks 60 a, 60 b are freelyslidable in the axial direction, and a shift drum 63 for making the endportions of the shift forks 60 a, 60 b slide along grooves 62 a, 62 b.The driving gears 58 a, 58 b, 58 c and 58 d are respectively engagedwith the driven gears 59 a, 59 b, 59 c and 59 d in this order. When thedriving gear 58 b slides to the right or left, a dog tooth on the sidesurface of the driving gear 58 b is engaged with the adjacent drivinggear 58 c or 58 a, and when the driven gear 59 c slides to the right orleft, a dog tooth on the side surface of the driven gear 59 c is engagedwith the adjacent driven gear 59 d or 59 b.

The driving gears 58 a and 58 c are held to be freely rotatable aroundthe main shaft 56, and the driven gears 59 b, 59 d are held to be freelyrotatable around the countershaft 57. The driving gear 58 b and thedriven gear 59 c are spline-coupled with the main shaft 56 and thecountershaft 57 and slidable in the axial direction. The driving gear 58d and the driven gear 59 a are fixed to the main shaft 56 and thecountershaft 57.

When the shift drum 63 is driven to be rotated by the actuator mechanism54, the shift forks 60 a, 60 b are moved in the axial direction alongthe grooves 62 a, 62 b of the shift drum 63, and the driving gear 58 band the driven gear 59 c slide in accordance with the shift stage.

In the transmission 50, a neutral state or power transmission whichselectively uses a transmission gear pair of any one of 1-speed to4-speed can be established between the main shaft 56 and thecountershaft 57 in accordance with the slide of the driving gear 58 band the driven gear 59 c.

The main shaft 56 and the countershaft 57 are freely rotatably held bybearings 64 a, 64 b, 66 a, 66 b.

A sprocket 67 is provided to the end portion of the countershaft 57, andthe sprocket 67 transmits rotation to the rear wheel 13 through thechain 15. A vehicle speed sensor 68 for detecting the rotational speedof the countershaft 57 in a contactless style is provided in theneighborhood of the countershaft 57. The rotational speed of thecountershaft 57 detected by the vehicle speed sensor 68 represents thespeed of the vehicle.

The engine 21 has an input rotation sensor 45 for detecting the inputrotation speed from the crankshaft 23 to the clutch mechanism 51 forgear shift, and an output rotation sensor 46 for detecting the outputrotation speed of the main shaft 56. The motorcycle 10 has a throttleopening sensor (not shown) for detecting the opening degree of thethrottle of an intake device. The vehicle speed sensor 68, the inputrotation sensor 45, the output rotation sensor 46 and the throttleopening degree sensor supply the detection values to the control unit17.

FIG. 3 is a cross-sectional view showing the gear shift mechanism 53,the actuator mechanism 54, the clutch mechanism 51 for gear shift andthe clutch operating mechanism 52.

Referring to FIGS. 2 and 3, the actuator mechanism 54 has a motor 70, ashift spindle 71 extending in the vehicle width direction in thecrankcase 30, and a train of gears (not shown) that decelerates therotation of the motor 70 and drives the shift spindle 71.

The shift spindle 71 is pivotally supported at both the ends thereof bythe left side wall 30 e of the crankcase 30 c and the crankcase cover 30d, and it is also pivotally supported at the intermediate portionthereof by an intermediate wall portion 30 f for supporting a bearing 64b of the main shaft 56. The crankcase cover 30 d is provided with anangle sensor 72 for detecting the rotation position of the shift spindle71.

The gear shift mechanism 63 has a gear shift arm 73 supported by theshift spindle 71, and a power storage mechanism 74 that stores the powerof the rotation of the shift spindle 71 and releases the stored power toturn the gear shift arm 73.

The gear shift arm 73 is connected to a shift drum 63, and the gearshift arm 73 is turned by the actuator mechanism 54, whereby the shiftdrum 63 is rotated and the gear shift is performed.

The power storage mechanism 74 has a turning arm 75 which is provided onthe shaft of the shift spindle 71 so as to be rotatable relatively tothe shift spindle 71, a return spring 76 which urges the gear shift arm73 to a neutral position, a stopper collar which is fixed onto the shaftof the shift spindle 71 and rotates integrally with the shift spindle71, a power storage collar 78 which is fixed onto the shaft of the shiftspindle 71 at a position which is away from the stopper collar 77 in theaxial direction and rotates integrally with the shift spindle 71, a pairof spring collars 79 a, 79 b which are provided on the shaft between thepower storage collar 78 and the stopper collar 77 so as to be rotatablerelatively to the shift spindle 71, and a power storage spring 80 whichis provided so as to be wound around the outer peripheries of the springcollars 79 a, 79 b.

The turning arm 75 has an inner cylindrical portion 75 a fitted to theouter peripheral surface of the shift spindle 71, an arm-side hookportion 75 b which projects in the axial direction from the outerperipheral surface of the inner cylindrical portion 75 a to the powerstorage spring 80 side, a press portion 75 c which projects in the axialdirection from the outer peripheral surface of the inner cylindricalportion 75 a to the opposite side to the arm-side hook portion 75 b, anda dog hole 75 d which is opened to the stopper collar 77 side. The gearshift arm 73 has an outer cylindrical portion 73 a fitted to the outerperipheral surface of the inner cylindrical portion 75 a of the turningarm 75, and an arm portion 73 b extending outwards in the peripheraldirection from the outer cylindrical portion 73 a.

The gear shift arm 73 is provided rotatably relatively to the turningarm 75, and the press portion 75 c of the turning arm 75 is insertedinto a restricting opening portion 73 c formed in the arm portion 73 bof the gear shift arm 73.

The return spring 76 is a helical torsion spring, and provided so as tobe wound around the outer cylindrical portion 73 a of the gear shift arm73 to urge the gear shift arm 73 to the neutral position through thepress portion 75 c. Here, the neutral position is a position under anormal state where the gear shift operation is not carried out. When theturning arm 75 is turned by only a predetermined angle, the restrictingopening portion 73 c presses the inner edge portion of the restrictingopening portion 73 c, and turns the gear shift arm 73. A pin 88 erectedfrom the intermediate wall portion 30 f is inserted in the restrictingopening portion 73 c, and the pin 88 restricts the turning range of thegear shift arm 73 through the restricting opening portion 73 c.

The stopper collar 77 has a dog tooth 77 a inserted in the dog hole 75 dof the turning arm 75. When the stopper collar 77 rotates by only apredetermined angle in connection with the rotation of the shift spindle71, the dog tooth 77 a urges the turning arm 75 in the rotationaldirection through the inner edge of the dog hole 75 d.

The power storage collar 78 has a collar-side hook portion 78 aprojecting in the axial direction to the power storage spring 80 side,and a clutch-side dog tooth 78 b projecting in the axial direction tothe opposite side to the collar-side hook portion 78 a.

The power storage spring 80 is a helical torsion spring. One end of thepower storage spring 80 is hooked to the arm-side hook portion 75 b ofthe turning arm 75, and the other end of the power storage spring 80 ishooked to the collar-side hook portion 78 a of the power storage collar78.

The gear shift arm 73 and the turning arm 75 are constrained by theclutch mechanism 51 for gear shift by the transmission 50 and thusunturnable on the shift spindle 71 while the clutch mechanism 51 forgear shift is set to the engaged state and the driving force occurs inthe transmission 50. When the shift spindle 71 is turned by the actuatormechanism 54 under the above state, the power storage collar 78 rotatesrelatively to the turning arm 75, and the power storage spring 80 isdeformed because one end thereof is kept to be fixed to the arm-sidehook portion 75 b side and the other end thereof at the collar-side hookportion 78 a side is turned, whereby power storage is started.Thereafter, when the clutch mechanism 51 for gear shift is released, thegear shift arm 73 and the turning arm 75 are allowed to be turnable, andthe stored power is released, so that the gear shift arm 73 is pressedand turned through the press portion 75 c of the turning arm 75 which isturned by the stored power of the power storing spring 80, whereby theshift drum 63 is rotated and the gear shift is performed.

When it is detected on the basis of the detection result of the anglesensor 72 that the gear shift is completed, the shift spindle 71 isinversely rotated, the gear shift arm 73 is returned to an originalposition, and the clutch mechanism 51 for gear shift is engaged.

In connection with the power storage, the power storing spring 80 isdeformed so that the axial line of the coil-shaped portion thereof isinclined with respect to the axial line of the shift spindle 71, andboth the end portions 80 a, 80 b of the coil-shaped portion come intocontact with the spring collars 79 a, 79 b bisected in the axialdirection, respectively. Specifically, those portions of both the endportions 80 a, 80 which are different in the peripheral direction bysubstantially 180° come into contact with the spring collars 79 a, 79 b.In the first embodiment, the spring collars 79 a, 79 b are configured tobe divided in the axial direction and turnable relatively to each other.Therefore, when both the end portions 8 a, 80 b come into contact withthem, the spring collars 79 a, 79 b rotates independently of each otherto release power. Therefore, friction when the power storage spring 80is twisted to store power can be reduced, and power can be smoothlystored.

The clutch operating mechanism 52 has a clutch lever 81 which ispivotally supported turnably on the shift spindle 71, a support shaft 82which is fixed to the inner surface of the crankcase cover 30 d in asubstantially coaxial positional relationship the main shaft 56, aplate-shaped base member 83 fixed to the support shaft 82, a lifter camplate 84 as an operating member which is connected to the clutch lever81 and provided to confront the base member 83, and plural balls 85which are pinched between the lifter cam plate 84 and the base member83.

The clutch lever 81 has a cylindrical portion 81 a which is provided onthe shift spindle 71 so as to be adjacent to the power storage collar78, and a lever portion 81 b extending outwards in the radial directionfrom the cylindrical portion 81 a. A clutch-side dog hole 81 c withwhich the clutch-side dog tooth 78 b of the power storage collar 78 isengaged is formed in the cylindrical portion 81 a.

The lifter cam plate 84 has a connection portion 84 a connected to thepin 86 which is provided to the tip of the lever portion 81 b of theclutch lever 81, and a press operating portion 84 b which faces the basemember 83. Cam portions 84 c, 83 a which are configured to have slopedfaces are formed on the mutually confronting faces of the pressoperation portion 84 b and base member 83, and the ball 85 is pinchedbetween the cam portions 84 c, 83 a. The guide shaft 83 b of the basemember 83 is fitted in the guide hole 84 d provided at the center of thelifter cam plate 84, whereby the movement in the axial direction of thelifter cam plate 84 is guided. Furthermore, a ball bearing 87 isprovided at the tip portion of the press operating portion 84 b, and thelifter cam plate 84 is connected to the clutch mechanism 51 for gearshift through the ball bearing 87.

When the clutch lever 81 is turned, the lifter cam plate 84 is turnedaround the guide shaft 83 b through the pin 86, and the cam portion 84 cslips on the ball 85, whereby the lifter cam plate moves in the axialdirection. Interlocking with the movement in the axial direction of thelifter cam plate 84, the clutch mechanism 51 for gear shift is engagedor released. The clutch-side dog hole 81 c of the clutch lever 81 has alarger width in the peripheral direction than the clutch-side dog tooth78 b of the power storage collar 78, and the clutch-side dog tooth 78 bdoes not press the clutch dog hole 81 c in the peripheral direction andturns the clutch lever 81 until the power storage collar 78 is rotatedby only a predetermined angle. Here, the predetermined angle of thepower storage collar 78 is set to be larger than an angle at which thepower storage spring 80 can store sufficient power. That is, in thefirst embodiment, after the power storage of the power storing spring 80is completed, the clutch lever 81 is turned, and the clutch mechanism 51for gear shift is released, so that stored power is released. Therefore,the gear shift can be quickly performed.

FIG. 4 is a cross-sectional view showing the clutch mechanism 51 forgear shift.

As shown in FIGS. 2 to 4, a primary driven gear 69 which is engaged withthe primary gear 37 of the crankshaft 23 is pivotally supported at theshaft end of the main shaft 56 so as to be rotatable relatively to themain shaft 56.

The clutch mechanism 51 for gear shift has a cup-shaped clutch outer 91fixed to the primary driven gear 69, a clutch center 92 which isprovided at the inside of the clutch outer 91 in the radial directionand integrally fixed to the main shaft 56, a pressure plate 93 whichmovable in the axial direction of the main shaft 56, a clutch plate 94provided between the pressure plate 93 and the clutch center 92, a mainspring 95 for urging the pressure plate 93 in the clutch engagingdirection, a lifter plate 96 for moving the pressure plate 93 in theclutch releasing direction, a sub spring 97 pinched between the lifterplate 96 and the clutch center 92, and a judder spring 98 pinchedbetween the clutch plate 94 and the pressure plate 93. The clutch center92 and the pressure plate 93 are assembled and unified, and constitutesa clutch inner 90 disposed inside the clutch outer 91.

The clutch outer 91 has a disc portion 91 a which is integrally fixed tothe outer surface of the primary driven gear 69, and an outercylindrical portion 91 b extending from the peripheral edge portion ofthe disc portion 91 a in a substantially coaxial positional relationshipwith the main shaft 56. The clutch outer 91 is rotatable relatively tothe main shaft 56 integrally with the primary driven gear 69. The clutchcenter 92 has a cylindrical hub portion 92 a fixed to the main shaft 56,and a disc-shaped receiving plate portion 92 b extending outwards in theradial direction from the axial end portion of the hub portion 92 a tilla neighborhood of the inner peripheral surface of the clutch outer 91. Asupport hole 92 c in which a part of the pressure plate 93 is insertedis formed in the receiving plate portion 92 b. A plurality of supportholes 92 c are formed to be arranged in the peripheral direction of thereceiving plate portion 92 b. Furthermore, the receiving plate portion92 b has a reception face 92 d which is provided at the outer peripheralportion of the receiving plate portion 92 b and receives the clutchplate 94, and has a spring holding convex portion 92 e which is providedon the surface opposite to the reception surface 92 d and annularlyprojects to the lifter plate 96 side along the outer peripheral portion.The clutch center 92 is fixed to the main shaft 56 by spline engagementand a nut 89, so that it is unrotatable relatively to the main shaft 56and unmovable in the axial direction.

The pressure plate 93 has an inner disc portion 93 a which is disposedto confront the receiving plate portion 92 b of the clutch center 92inside the clutch outer 91, an inner cylindrical portion 93 b whichextends from the peripheral edge portion of the inner disc portion 93 ato the disc portion 91 a side of the clutch outer 91 in a substantiallycoaxial positional relationship with the main shaft 56, and a pressplate portion 93 c extending outwards in the radial direction from thetip portion of the inner cylindrical portion 93 b to a neighborhood ofthe inner peripheral surface of the clutch outer 91. The pressure plate93 is formed to be rotatable relatively to the clutch center 92 by onlya predetermined rotational angle.

A fitting hole 93 d which is freely slidably fitted to the outerperipheral surface of the hub portion 92 a of the clutch center 92 isformed in the inner disc portion 93 a. A release boss 99 whichpenetrates through the support hole 92 c of the clutch center 92 andextends to the lifter plate 96 side is formed around the fitting hole 93d in the inner disc portion 93 a.

A plurality of release bosses 99 are formed to be arranged atsubstantially equal intervals in the peripheral direction of the innerdisc portion 93 a. The release boss 99 has a column portion 99 ainserted in the support hole 92 c and a guide shaft portion 99 b formedto be smaller in diameter than the column portion 99 a at the tipportion, and a step portion 99 c having a larger diameter than the guideshaft portion 99 b is formed at the boundary portion between the guideshaft portion 99 b and the column portion 99 a.

A stopper plate 105 constructed by a washer having a larger diameterthan the guide shaft portion 99 b is provided to the tip surface of theguide shaft portion 99 b, and the stopper plate 105 is fixed to therelease boss 99 by a fixing bolt which is screwed to the tip surface ofthe guide shaft portion 99 b.

The clutch plate 94 has outer friction plates 94 a provided to theclutch outer 91, and inner friction plates 94 b provided to the clutchcenter 92, and a plurality of outer friction plates 94 a and a pluralityof inner friction plates 94 b are alternately stacked and arrangedbetween the pressure plate 93 and the clutch center 92. Each outerfriction plate 94 a is supported on the outer cylindrical portion 91 bof the clutch outer 91 through spline engagement, and it is provided soas to be movable in the axial direction of the clutch outer 91 andunrotatable relatively to the clutch outer 91.

Each inner friction plate 94 b is supported on the outer peripheralsurface of the inner cylindrical portion 93 b of the pressure plate 93through spline engagement, and it is provided so as to be movable in theaxial direction of the pressure plate 93 and unrotatable relatively tothe pressure plate 93.

An outer friction plate 94 a 1 which is directly in contact with thepress plate portion 93 c of the pressure plate 93 out of the outerfriction plates 94 a is larger in diameter at the inner peripheralportion 100 thereof than the other outer friction plates 94 a, and ajudder spring 98 is provided between the inner peripheral portion 100and the inner cylindrical portion 93 b. The judder spring 98 is aring-shaped disc spring, and presses each inner friction plate 94 b andeach outer friction plate 94 a except for the outer friction plate 94 a1 to the receiving plate portion 92 b side of the clutch center 92.

A plate-shaped back torque limit member 101 is fixed to the inner discportion 93 a inside the inner cylindrical portion 93 b of the pressureplate 93. The back torque limit member 101 is fixed by a bolt 108 whichis provided coaxially with the fixing bolt 106.

The back torque limit member 101 and a lifter pin 120 fixed to thereceiving plate portion 92 b of the clutch center 92 constitutes a backtorque limiter mechanism. The back torque limiter mechanism is apublicly known technique disclosed in JP-H08-93786, for example, and itis a mechanism for setting the clutch from the engagement state to ahalf clutch (partial engagement) state when a torque having apredetermined value or more acts in the opposite direction to powertransmission in a forward direction.

The back torque limit member 101 has a cam portion 101 b whichpenetrates through the pressure plate 93 and is fitted to the lifterpin. When back torque of a predetermined value or more acts from therear wheel 13 side, the pressure plate 93 rotates relatively to theclutch center 92, whereby the cam portion 101 b slides on the lifter pin120, and the pressure plate 93 moves in the clutch release direction.According to the back torque limit mechanism, shift shock caused by backtorque can be reduced.

A ring-shaped clip 102 is press-fitted in the outer peripheral surfaceat the disc portion 91 a side of the hub portion 92 a of the clutchcenter 92, and the clip 102 supports a ring-shaped retainer 103 forreceiving the main spring 95.

The main spring 95 is a ring-shaped disc spring, and pinched between theback torque limit member 101 at the pressure plate 93 side and theretainer 103. Specifically, the main spring 95 is disposed between thehub portion 92 a of the clutch center 92 and the inner cylindricalportion 93 b of the pressure plate 93, and the outer diameter portion ofthe main spring 95 is supported by the back torque limit member 101through the spring receiving member 101 a while the inner diameterportion of the main spring 95 is supported by the retainer 103.

The main spring 95 urges the pressure plate 93 in the direction alongwhich the clutch plate 94 is pinched by the pressure plate 93 and theclutch center 92, that is, in the clutch engaging direction.

The lifter plate 96 is formed to be disc-shaped, and disposed betweenthe clutch center 92 and the lifter cam plate 84 (FIG. 3). The lifterplate 96 has a bearing support hole portion 96 a in which a ball bearing87 is fitted, and a hole portion 96 b in which the release boss 99 ofthe pressure plate 93 is inserted.

The outer wheel of the ball bearing 87 is fitted in the bearing supporthole portion 96 a, and the inner wheel of the ball bearing 87 is fittedon the outer peripheral surface of the press operation portion 84 b ofthe lifter cam plate 84. Therefore, the lifter plate 96 is movable inthe axial direction together with the lifter cam plate 84, and rotatablerelatively to the lifter cam plate 84.

The hole portion 96 b is a hole having a smaller diameter than thestopper plate 105 and the step portion 99 c, and a contact face 96 cwhich is substantially parallel to the step portion 99 c is formed atthe peripheral edge portion of the hole portion 96 b.

A plurality of hole portions 96 b are formed around the bearing supporthole portion 96 a provided to the center portion of the lifter plate 96.Each hole portion 96 b is fitted to the guide shaft portion 99 b of eachrelease boss 99. Each hole portion 96 b is fitted to the guide shaftportion 99 b, and then the stopper plate 105 and the fixing bolt 106 arefixed, whereby the lifter plate 96 is connected to the pressure plate93.

The lifter plate 96 has a sub spring receiving portion 96 d forreceiving the sub spring 97 on a surface thereof which confronts thereceiving plate portion 92 b of the clutch center 92. The sub springreceiving portion 96 d is located at an outside of each hole portion 96b in the radial direction.

The sub spring 97 is a ring-shaped disc spring, and pinched between thesub spring receiving portion 96 d of the lifter plate 96 and thereceiving plate portion 92 b of the clutch center 92. Specifically, theouter diameter portion of the sub spring 97 is supported by the clutchcenter 92 through a supporting member 107 a disposed at the inside ofthe spring holding convex portion 92 e, and the inner diameter portionof the sub spring 97 is supported by the lifter plate 96 through asupporting member 107 b disposed at the sub spring receiving portion 96d.

The sub spring 97 urges the lifter plate 96 in such a direction that thelifter plate 96 comes into contact with a stopper plate 96 while theclutch center 92 fixed to the main shaft serves as a spring seat. Theurging force of the sub spring 97 is transmitted to a pressure plate 93through the lifter plate 96, the stopper plate 105 and the fixing bolt106, and the pressure plate 93 presses the clutch plate 94 in such a waythat the pressure plate 93 is pulled to the sub spring 97 side. That is,the urging direction of the sub spring 97 is identical to the urgingdirection of the main spring 95, which is the clutch engagementdirection.

The lifter plate 96 also functions as a sub pressure plate for urgingthe pressure plate 93 in the clutch engagement direction through the subspring 97.

Under the clutch engagement state, the clutch plate 94 is pinched by theurging force of the main spring 95 and the sub spring 97, and therotation of the clutch outer 91 which is rotated by the primary gear 37is enabled to be transmitted to the clutch center 92 through the clutchplate 94, so that the main shaft 56 is rotated integrally with theclutch center 92.

When the pressure plate 93 is moved against the urging force of the mainspring 95 and the sub spring 97 through the lifter cam plate 84, thepinching of the clutch plate 94 is released, whereby the clutch releasestate is set.

The thickness of the portion corresponding to the contact face 96 c ofthe lifter plate 96 is set to be smaller than the length of the guideshaft portion 99 b, and a gap G is formed between the step portion 99 cof the release boss 99 and the contact face 96 c under the clutchengagement state.

When the clutch lever 81 is turned in connection with the shift spindle71 and thus the lift cam plate 84 is moved in the axial direction, thelifter plate 96 is pressed through the ball bearing 87 and lifted so asto be away from the stopper plate 105, whereby the lifter plate 96 ismoved to the clutch center 92 side so that the gap G is reduced.

FIG. 5 is an example of a diagram showing the clutch capacity of theclutch mechanism 51 for gear shift.

As shown in FIG. 5, in the first embodiment, the capacity of the clutchmechanism 51 for gear shift is made variable by changing a spring whichcontributes to the clutch capacity. Specifically, the clutch capacity isvariable at plural stages among a maximum capacity at which the clutchcapacity is determined by the urging force of the main spring 95 and thesub spring 97, an intermediate capacity at which the clutch capacity isdetermined by the urging force of the main spring 95 and a smallcapacity at which the clutch capacity is determined by the urging forceof the judder spring 98 pressed by the main spring 95.

The maximum capacity of the clutch capacity is obtained under the clutchengagement state shown in FIG. 4, and under this state, the lifter plate94 is in contact with the stopper plate 105, and the urging force of thesub spring 97 is transmitted to the pressure plate 93 through the lifterplate 96 and the stopper plate 105. Therefore, the urging force of thepressure plate 93 with which the clutch plate 94 is pressed is equal tothe sum of the urging force of the main spring 95 and the urging forceof the sub spring 97, and thus it becomes the maximum force.

That is, the lifter plate 96 and the stopper plate 105 constitutes a subspring load transmission passage S for transmitting the urging force ofthe sub spring 97 to the pressure plate 93.

FIG. 6 is a cross-sectional view showing the clutch mechanism 51 forgear shift under the intermediate capacity state. When the lifter camplate 84 is moved in the clutch release direction in connection with therotation of the shift spindle 71 by the actuator mechanism 54 (FIG. 3),the lifter plate 96 is lifted against the urging force of the sub spring97 to the step portion 99 c side along the guide shaft portion 99 b, andseparated from the stopper plate 105 as shown in FIG. 6.

The lifter plate 96 is separated from the stopper plate 105, so that thesub spring load transmission passage S is cut off, the urging force ofthe sub spring 97 is not transmitted to the pressure plate 93, and theclutch capacity is determined by only the main spring 95. Therefore, asshown in FIG. 5, the clutch capacity decreases from the maximum capacityto the intermediate capacity instantaneously when the lifter plate 96separates from the stopper plate 105. A first predetermined lift amountL1 (first predetermined amount) of the lifter plate 96 at which the subspring load transmission passage S is cut off may be set to be largerthan zero, and it is determined by the dimensional precision of eachpart, etc.

When the movement of the lifter cam plate 84 is continued after thelifter plate 96 separates from the stopper plate 105, the lifter plate96 continues to further move to the step portion 99 c side. The sectionfrom the separation of the lifter plate 96 from the stopper plate 105till the contact of the lifter plate 96 with the step portion 99 ccorresponds to an intermediate-capacity section. In this section, thelifter plate 96 merely moves relatively to the step portion 99 c, andhas no effect on the load of the main spring 95. Therefore, as shown inFIG. 5, the clutch capacity is determined by only the main spring 95 inthe intermediate-capacity section, and the intermediate capacity isfixed. In the first embodiment, a backlash based on the gap G isprovided. The section in which the intermediate capacity is obtained canbe set to be long, and the clutch capacity can be made variable withoutany highly precise part and control method.

FIG. 7 is a cross-sectional view showing the clutch mechanism 51 forgear shift under the small-capacity state. When the lifter plate 96 ismoved by only a second predetermined lift amount L2 (secondpredetermined amount) by the lifter cam plate 84 and thus the lifterplate 96 comes into contact with the step portion 99 c as shown in FIG.7, the pressure plate 93 is pressed by the lifter plate 96, and moves inthe clutch release direction against the urging force of the main spring95. A small-capacity section is the section from the contact of thelifter plate 96 with the step portion 99 c till the perfect release ofthe clutch.

When the pressure plate 93 moves and the press plate portion 93 cseparates from the outer friction plate 94 a 1, the judder spring 98determines the clutch capacity. The judder spring 98 presses the clutchplates 94 excluding the outer friction plate 94 a 1 through the innerfriction plate 94 b which is adjacent to the outer friction plate 94 a1. The compression state of the judder spring 98 is gradually releasedas the pressure plate 93 moves to the clutch release direction, so thatthe clutch capacity in the small-capacity section moderately decreases.Therefore, the torque variation in the neighborhood of the clutchrelease can be suppressed, and thus shift shock can be reduced. When thejudder spring 98 separates from the pressure plate 93 or the clutchplate 94, the clutch capacity is equal to zero.

When automatic transmission is performed, the control unit 17 operatesthe actuator mechanism 54 on the basis of the torque of the countershaft57, and selects the clutch capacity which can reduce the shift shock.For example, when shift-up from 1-speed to 2-speed is performed, thecontrol unit 17 selects the clutch capacity of the maximum capacity orthe intermediate capacity on the basis of the detected torque of thecountershaft 57 before gear shift so as to reduce the shift shock, andengages the clutch mechanism 51 for gear shift with the selected clutchcapacity after the train of gears of the transmission 50 is shifted.Specifically, as shown at the left side of the paper surface of FIG. 16,the clutch capacity is selected so that the clutch capacity of theclutch mechanism 51 for gear shift is not so away from the gap betweenthe countershaft torque before gear shift and the countershaft torqueafter gear shift or the band thereof.

Accordingly, the difference in rotation between the countershaft 57 sideand the crankshaft 23 side can be properly absorbed by the clutchmechanism 51 for gear shift, and the shift shock can be reduced. Here,the toques of the countershaft 57 before and after gear shift aredetermined on the basis of a map in which the relationship of the enginespeed, the throttle opening degree and the toque of the countershaft 57is stored, for example.

As described above, according to the first embodiment to which thepresent invention is applied, the sub spring 97 for urging the pressureplate 93 in the clutch engagement direction through the lifter plate 96is provided between the clutch center 92 fixed in the axial direction ofthe main shaft 56 and the lifter plate 96 for lifting the pressure plate93 in the clutch release direction, and the urging force of the subspring 97 to the pressure plate 93 is cut off by lifting the lifterplate 96 by the first predetermined lift amount L1 or more. Therefore,the clutch engaging load can be secured by the main spring 95 and thesub spring 97 which act in the clutch engagement direction, and also thelifter plate 96 is lifted under gear shift, whereby the urging force ofthe sub spring 97 to the pressure plate 93 is cut off, and theengagement load of the clutch can be produced by only the main spring95. Accordingly, the clutch capacity can be set to plural stages of themaximum capacity under the clutch engagement state and the intermediatecapacity under the state that the lifter plate 96 is lifted, so that theclutch mechanism 51 for gear shift in which the shift shock can bereduced by changing the clutch capacity can be implemented with a simpleconstruction. According to the clutch mechanism 51 for gear shift, evenwhen the system parts for controlling the intermediate capacity of theclutch and the control method are relatively simple, the intermediatecapacity of the clutch can be easily matched with a set value.

The pressure plate 93 is provided with the release boss 99 extending tothe lifter plate 96 side, and the stopper plate 105 fixed to the endportion of the release boss 99, the lifter plate 96 is provided with thehole portion 96 having a smaller diameter than the stopper plate 105,and the release boss 99 is inserted in the hole portion 96 b. Therefore,the construction of cutting off the urging force of the sub spring 97 tothe pressure plate 93 can be implemented with reducing the number ofparts at maximum. Furthermore, the lifter plate 96 functions as a subpressure plate which is separate from the pressure plate 93 anddisplaceable relatively to the pressure plate 93, the sub spring loadtransmission passage S is provided so that the sub spring 97 presses thepressure plate 93 through the lifter plate 96, and the lifter plate 96separates from the stopper plate 105 of the pressure plate 93 when thelifter plate 96 lifts by the first predetermined lift amount or more,thereby cutting off the sub spring load transmission passage S.Therefore, the sub spring load transmission passage S can be providedwith a simple construction.

The clutch mechanism 51 for gear shift has the clutch outer 91 disposedat the outside of the clutch center 92 in the radial direction, and theplural clutch plates 94 are configured so that the outer friction plates94 a provided to the clutch outer 91 and the inner friction plates 94 bprovided to the clutch center 92 are alternately arranged between theclutch center 92 and the pressure plate 93, the main spring 95 isdisposed at the opposite side to the lifter plate 96 in the axialdirection and between the hub portion 92 a of the clutch center 92 andthe pressure plate 93, and the main spring 95 and the sub spring 97 canbe disposed at both the sides of the clutch center 92. Therefore, thenumber of parts serving as seats of the main spring 95 and the subspring 97 can be reduced, and the main spring 95 and the sub spring 97can be compactly disposed. Furthermore, the sub spring 97 is disposed atthe outside of the release boss 99 of the pressure plate 93 in theradial direction and provided as a ring-shaped disc spring. Therefore,the sub spring 97 can be provided with a small number of parts, and thedegree of freedom for the design of the sub spring 97 can be secured byutilizing a space at the outside of the release boss 99 in the radialdirection, so that the load of the sub spring 97 can be easily secured.

The step portion 99 c having a larger diameter than the hole portion 96b of the lifter plate 96 is provided at the pressure plate 93 side ofthe release boss 99 of the pressure plate 93, and when the lifter plate96 is lifted by only the second predetermined lift amount L2, the lifterplate 96 comes into contact with the step portion 99 c, and directlymoves the pressure plate 93. Therefore, the clutch can be released witha simple construction while the construction for cutting off the urgingforce of the sub spring 97 is provided.

Furthermore, the judder spring 98 for urging the clutch plate 94 in theengagement direction is provided between the pressure plate 93 and theclutch plate 94. Therefore, in a state near to the clutch release state,the capacity of the clutch is determined by the judder spring 98, andgradually decreases due to the movement of the pressure plate 93 in theclutch release direction. Therefore, the clutch capacity can bemoderately reduced from the intermediate capacity to the clutch release,and the torque variation of the countershaft 57 can be moderated in theneighborhood of the clutch release state. Therefore, the shift shock canbe reduced.

The first embodiment described above is an example to which the presentinvention is applied, and the present invention is not limited to theabove embodiment.

In the first embodiment, the main spring 95 and the sub spring 97 aredescribed as the disc springs. However, the present invention is notlimited to this style, and they may be coil springs, for example. Theback torque limit member 101 is configured to be fixed to the pressureplate 93 by the bolt 108. However, the back torque limit member 101 maybe provided with a convex portion protruding in the radial direction,and a concave portion which is engaged with the convex portion may beformed in the pressure plate 93, whereby the back torque limit member101 is fixed to the pressure plate 93 by a circlip while the rotationthereof is stopped. The back torque limit member 101 and the pressureplate 93 are described as separate bodies. However, they may be formedintegrally with each other.

Second Embodiment

A second embodiment to which the present invention is applied will bedescribed hereunder with reference to FIGS. 8 to 11. In the secondembodiment, those parts which are configured to have the sameconstructions as the first embodiment are represented by the samereference numerals, and the descriptions thereof are omitted.

In the first embodiment, the sub spring 97 is pinched between the lifterplate 96 and the clutch center 92. However, the second embodiment isdifferent from the first embodiment in that a sub pressure plate 210which is separate from the lifter plate 296 is provided at the oppositeside to the lifter plate 296 through the pressure plate 293, and the subpressure plate 210 is urged by a sub spring 297 provided at the sameside as the main spring 295.

FIG. 8 is a cross-sectional view showing the clutch mechanism 251 forgear shift according to the second Embodiment.

The clutch mechanism 251 for gear shift has a clutch outer 91, a clutchcenter 292 which is provided at the inside of the clutch outer 91 in theradial direction and fixed integrally to the main shaft 56, a pressureplate 293 which is movable in the axial direction of the main shaft 56,a clutch plate 94 provided between the pressure plate 293 and the clutchcenter 292, a main spring 295 for urging the pressure plate 293 in aclutch engagement direction, a lifter plate 296 for moving the pressureplate 293 in a clutch release direction, a sub pressure plate 210 whichis provided at the inside of the pressure plate 293 in the radialdirection and movable in the axial direction relatively to the pressureplate 293, a sub spring 297 for urging the pressure plate 293 throughthe sub pressure plate 210 in the clutch engagement direction, and ajudder spring 98 pinched between the clutch plate 94 and the pressureplate 293. The clutch center 292 and the pressure plate 293 areassembled and unified, and disposed inside the clutch outer 91, therebyconstituting a clutch inner 290.

The lifter plate 296 is formed in a disc-shape, and disposed between theclutch center 292 and the lifter cam plate 84 (FIG. 3). The lifter plate296 has, at the center portion thereof, a bearing support hole portion296 a in which the ball bearing 87 is fitted.

The lifter plate 296 further has a release member 299 on a surfacethereof which faces the clutch center 292.

FIG. 9 is a plan view showing the release member 299.

The release member 299 has a flange ring 270 (flange portion) having alarger diameter than the hub portion 292 a of the clutch center 292, andrelease bosses 271 which are provided so as to penetrate through theplate-like flange ring 270 in the axial direction and erected from boththe surfaces of the flange ring 270.

A plurality of release bosses 271 are provided to be spaced from oneanother at substantially equal intervals in the peripheral direction ofthe flange ring 270.

Each release boss 271 is formed in a cylindrical shape, and the flangering 270 is provided at the center portions in the axial direction ofthe release bosses 271 to integrally connect the respective bosses 271.

The release member 299 is integrally fixed to the lifter plate 296 whilethe respective release bosses 271 arranged on the surface of the lifterplate 296 at the clutch center 292 side are fastened by a bolt 211inserted from the lifter cam plate 84 side into the lifter plate 296.The release bosses 271 press the sub pressure plate 210 by the pressfaces 271 a at the tips of the release bosses 271.

A release hole 270 a for releasing a lifter pin 120 and a lighteninghole 270 b are formed between the respective adjacent release bosses 271in the flange ring 270.

As shown in FIG. 8, the clutch center 292 has a cylindrical hub portion292 a fixed to the main shaft 56, and a disc-shaped receiving plateportion 292 b which extends outwards in the radial direction from theaxial end portion of the hub portion 292 a to a neighborhood of theinner peripheral surface of the clutch outer 91. Through-holes 292 cthrough which the release bosses 271 of the lifter plate 296 penetrateare formed in the receiving plate portion 292 b. A plurality ofthrough-holes 292 c are formed to be arranged in the peripheraldirection of the hub portion 292 a. The receiving plate portion 292 bhas a reception face 292 d for receiving the clutch plate 94 at an outerperipheral portion outside the through-holes 292 c.

The pressure plate 293 has an inner disc portion 293 a which is disposedto confront the receiving plate portion 292 b of the clutch center 292at the inside of the clutch outer 91, an inner cylindrical portion 293 bwhich extends from the peripheral edge portion of the inner disc portion293 a to the disc portion 91 a side of the clutch outer 91 in asubstantially coaxial positional relationship with the main shaft 56,and a press plate portion 293 c which extends outwards in the radialdirection from the tip portion of the inner cylindrical portion 293 b toa neighborhood of the inner peripheral surface of the clutch outer 91.The pressure plate 293 is formed to be rotatable relatively to theclutch center 292 by only a predetermined rotational angle so that backtorque is released.

A fitting hole 293 d which is freely slidably fitted to the outerperipheral surface of the hub portion 292 a of the clutch center 292 isformed at the center of the inner disc portion 293 a. Hole portions 293e in which the release boss 271 of the release member 299 is inserted isprovided around the fitting hole 293 d in the inner disc portion 293 a.A plurality of hole portions 293 e are arranged in the peripheraldirection of the inner disc portion 293 a. The flange ring 270 which islarger than the hole portion 293 e in the radial direction comes intocontact with the inner disc portion 293 a, whereby the position in theaxial direction of the release boss 271 is regulated. Each of the innerfriction plates 94 b is provided to the outer peripheral surface of theinner cylindrical portion 293 b.

A back torque limit member 212 is integrally fixed to the pressure plate293 inside the inner cylindrical portion 293 b of the pressure plate293. The back torque limit member 212 has a cylindrical portion 212 afitted to the inner peripheral surface of the inner cylindrical portion293 b, and a disc-shaped bottom plate portion 212 b which blocks thebottom portion of the cylindrical portion 212 a and is in contact withthe inner disc portion 293 a, and receives the main spring 295. Areceiving groove portion 212 d (a seat portion of the main spring)having an inner peripheral portion which is larger in diameter by onestage is formed at the tip portion of the cylindrical portion 212 a.

A plurality of tip through-holes 212 c through which the tip portions ofthe release bosses 271 penetrate are formed in the disc-shaped bottomportion 212 b, and a cam portion 101 b penetrating through the innerdisc portion 293 a is provided. The cam portion 101 b is engaged withthe lifter pin 120 fixed to the clutch center 292.

The main spring 295 is a ring-shaped disc spring, and pinched betweenthe back torque limit member 212 and the retainer 103 which is nearer tothe disc portion 91 a side than the back torque limit member 212.Specifically, the main spring 295 is disposed between the hub portion292 a of the clutch center 292 and the inner cylindrical portion 293 bof the pressure plate 293, and the outer diameter portion of the mainspring 295 is supported by the receiving groove portion 212 d while theinner diameter portion of the main spring 295 is supported by theretainer 103.

The main spring 295 urges the pressure plate 293 in the direction alongwhich the clutch plate 94 is pinched by the pressure plate 293 and theclutch center 292, that is, in the clutch engagement direction.

The sub pressure plate 210 has a sliding cylindrical portion 210 a whichis press-fitted in the inner diameter portion 212 e (inlay fitting hole)of the cylindrical portion 212 a of the back torque limit member 212,and a disc-shaped bottom plate portion 212 b which blocks the bottomportion of the sliding cylindrical portion 210 a. The bottom plateportion 210 b comes into contact with the disc-shaped bottom plateportion 212 b of the back torque limit member 212, and a part thereofcomes into contact with the press face 271 a of the release boss 271.The sub pressure plate 210 is movable in the axial direction relativelyto the pressure plate 293 inside the back torque limit member 212.

On the outer peripheral surface of the cylindrical hub portion 292 a ofthe clutch center 292, a ring-shaped clip 202 is inlaid between the mainspring 295 and the sub pressure plate 210, and the clip 202 supports aring-shaped retainer 203 for receiving the sub spring 297.

The sub spring 297 is a ring-shaped disc spring, and pinched between theretainer 203 and the bottom plate portion 210 b of the sub pressureplate 210. Specifically, the sub spring 297 is disposed between thesliding cylindrical portion 210 a and the hub portion 292 a, and theouter diameter portion of the sub spring 297 is supported by the seatportion 210 c at the outer peripheral side of the sub pressure plate 210while the inner diameter portion of the sub spring 297 is supported bythe retainer 203.

The sub spring 297 urges the pressure plate 293 through the sub pressureplate 210 and the back torque limit member 212 while the retainer 203fixed to the hub portion 292 a serves as a spring seat, thereby pressingthe clutch plate 94. That is, the urging direction of the sub spring 297is the same as the urging direction of the main spring 295, and itcorresponds to the clutch engagement direction.

In the clutch engagement state shown in FIG. 8, the urging force of thepressure plate 293 on the clutch plate 94 is equal to the sum of theurging force of the main spring 295 and the urging force of the subspring 297, and becomes the maximum value. The sub pressure plate 210and the back torque limit member 212 constitutes a sub spring loadtransmission passage S for transmitting the urging force of the subspring 297 to the pressure plate 293.

Under the clutch engagement state, the pressure plate 293 is pressed tothe clutch center 292 side by the urging force of the main spring 295and the sub spring 297. Furthermore, under this state, the lifter plate296 is pressed to the lifter cam plate 84 side by the urging force ofthe sub spring 297 through the sub pressure plate 210 and the releasebosses 271, and a gap G is formed between the flange ring 270 of therelease member 299 and the inner disc portion 293 a of the pressureplate 293. That is, under the clutch engagement state, the flange ring270 is separated from the inner disc portion 293 a, and located betweenthe inner disc portion 293 a and the receiving plate portion 292 b ofthe clutch center 292.

FIG. 10 is a cross-sectional view showing the clutch mechanism 251 forgear shift under the intermediate-capacity state.

When the lifter cam plate 84 is moved in the clutch release direction inconnection with the rotation of the shift spindle 71 by the actuatormechanism 54, as shown in FIG. 10, the release bosses 271 of the releasemember 299 are moved against the urging force of the sub spring 297, andthe bottom plate portion 210 b of the sub pressure plate 210 is pressedand lifted by the press face 271 a and thus separated from thedisc-shaped bottom plate portion 212 b of the back torque limit member212.

The bottom plate portion 210 b is separated from the disc-shaped bottomplate portion 212 b, whereby the sub spring load transmission passage Sis cut off, and the urging force of the sub spring 297 is nottransmitted to the pressure plate 293, so that the clutch capacity isdetermined by only the main spring 295. Therefore, as shown in FIG. 5,the clutch capacity decreases from the maximum capacity to theintermediate capacity instantaneously when the sub pressure plate 210separates from the disc-shaped bottom plate portion 212 b. A firstpredetermined lift amount L1 (first predetermined amount) of the lifterplate 296 at which the sub spring load transmission passage S is cut offmay be set to be larger than zero, and it is determined by thedimensional precision of each part or the like.

When the movement of the lifter cam plate 84 is continued after thebottom plate portion 210 b separates from the disc-shaped bottom plateportion 212 b, the lifter plate 296 continues to further move to thepressure plate 293 side. The section from the separation of the bottomplate portion 210 b from the disc-shaped bottom plate portion 212 b tillthe contact of the flange ring 270 of the release member 299 with theinner disc portion 293 a corresponds to an intermediate-capacitysection. In this section, the sub pressure plate 210 is merely movedrelatively to the pressure plate 293, and has no effect on the load ofthe main spring 295. Therefore, as shown in FIG. 5, the clutch capacityis determined by the main spring 295 and the intermediate capacity isfixed in this intermediate-capacity section. In the second embodiment,since a backlash based on the gap G is provided, the section in whichthe intermediate capacity is obtained can be lengthened, and the clutchcapacity can be made variable without providing any high-precision partand control method.

When the lifter plate 296 is moved by only a second predetermined liftamount (second predetermined amount) by the lifter cam plate 84 and thusthe flange ring 270 comes into contact with the inner disc portion 293 aof the pressure plate 293 (not shown), the pressure plate 293 is pressedby the flange ring 270, and moved in the clutch release directionagainst the urging force of the main spring 295 and the sub spring 297.A small-capacity section corresponds to the section from the contact ofthe flange ring 270 with the inner disc portion 293 a till the perfectrelease of the clutch.

When the pressure plate 293 moves and the press plate portion 293 cseparates from the external friction plate 94 a 1, the clutch capacityis determined by the judder spring 98.

As described above, according to the second embodiment to which thepresent invention is applied, there is provided the sub pressure plate210 which is separate from and movable relatively to the pressure plate293 which is displaceable in the axial direction of the main shaft 56,the sub spring 297 for pressing the pressure plate 293 in the clutchconnection direction through the sub pressure plate 210 is provided, andwhen the lifter plate 296 is lifted by only the first predetermined liftamount L1, the sub pressure plate 210 is separated from the pressureplate 293, thereby cutting off the sub spring load transmission passageS to the pressure plate 293. Therefore, the clutch engaging load can besecured by the main spring 295 and the sub spring 297 which act in theclutch connection direction, and when the lifter plate 296 is liftedunder gear shift, the sub spring load transmission passage S to thepressure plate 293 can be cut off, so that the clutch engaging load canbe produced by only the main spring 295. Accordingly, the clutchcapacity can be set at multiple stages of the maximum capacity under theclutch engagement state and the intermediate capacity under the statethat the lifter plate 296 is lifted. Therefore, the clutch mechanism 251for gear shift that can reduce the shift shock by making the clutchcapacity variable can be implemented with a simple construction.

Furthermore, the sub spring 297 and the sub pressure plate 210 aredisposed at the opposite side to the lifter plate 296 through thepressure plate 293, the pressure plate 293 is provided with the holeportion 293 e, the lifter plate 296 is provided with the release bosses271 inserted in the hole portion 293 e, and when the lifter plate 296 islifted by the first predetermined lift amount L1 or more, the releasebosses 271 come into contact with the sub pressure plate 210, wherebythe sub pressure plate 210 separates from the pressure plate 293.Therefore, even when the sub spring 297 is configured to be disposed atthe opposite side to the lifter plate 296, the cut-off mechanism for thesub spring load transmission passage S can be provided with a simpleconstruction.

The flange ring 270 having a larger diameter than the hole portion 293 eof the pressure plate 293 is provided to the intermediate portion in theaxial direction of the release bosses 271 of the lifter plate 296, andwhen the lifter plate 296 is lifted by only the second predeterminedamount, the flange ring 270 comes into contact with the pressure plate293 and directly moves the pressure plate 293. Therefore, the clutch canbe released with a simple construction even in the construction that thesub spring load transmission passage S is provided.

Furthermore, the sub spring 297 and the sub pressure plate 210 aredisposed between the hub portion 292 a of the clutch center 292 and thepressure plate 293, and the main spring 295 is disposed to be nearer tothe clutch outer 91 side than the sub spring 297 and between the hubportion 292 a of the clutch center 292 and the pressure plate 293, sothat the main spring 295 and the sub spring 297 can be compactlydisposed at the same side.

Still furthermore, the sub spring 297 and the main spring 295 areprovided as ring-shaped disc springs, the sub pressure plate 210 isinlaid in the pressure plate 293, the seat portion 210 c of the subspring 297 is provided at the outside in the radial direction, and thepressure plate 293 is provided with the receiving groove portion 212 dof the main spring 295 at the outside in the radial direction of theinner diameter portion 212 e in which the sub pressure plate 210 isfitted. Therefore, the sub spring load transmission passage S and thecut-off mechanism therefor can be provided with simple constructions.Furthermore, the main spring 295 can be enlarged, so that the load ofthe main spring 295 can be easily secured.

The second embodiment is an example to which the present invention isapplied, and the present invention is not limited to the aboveembodiment.

In the second embodiment, the respective release bosses 271 areintegrally connected to one another by the flange ring 270. However, thepresent invention is not limited to this construction. For example, thesecond embodiment may be modified so that the flange ring 270 is notprovided, a flange portion having a larger diameter than the holeportion 293 e is formed at the intermediate portion in the axialdirection of each release portion 271, and the pressure plate 293 ispressed by the flange portions.

Third Embodiment

A third embodiment to which the present invention is applied will bedescribed hereunder with reference to FIGS. 11 to 15. In the thirdembodiment, the same constructions as the first embodiment arerepresented by the same reference numerals, and the descriptions thereofare omitted.

In the first embodiment, it is described that the sub spring 97 ispinched between the lifter plate 96 and the clutch center 92. However,the third embodiment is different from the first embodiment in that asub pressure plate 310 which is separate from the lifter plate 396 ismainly provided at the opposite side to the lifer plate 396 through apressure plate 393, the sub pressure plate 310 is urged by a sub spring397 provided at the same side as a main spring 395, and the main spring395 and the sub spring 397 are configured as coil springs.

FIG. 11 is a cross-sectional view showing a clutch mechanism 351 forgear shift according to the third embodiment.

The clutch mechanism 351 for gear shift has a clutch outer 91, a clutchcenter 392 which is provided inside the clutch outer 91 in the radialdirection and integrally fixed to a main shaft 56, a pressure plate 393which is movable in the axial direction of the main shaft 56, a clutchplate 94 provided between the pressure plate 393 and the clutch center392, a main spring 395 for urging the pressure plate 393 in a clutchengagement direction, a lifter plate 396 for moving the pressure plate393 in a clutch release direction, a sub pressure plate 310 which isprovided inside the pressure plate 393 in the radial direction andmovable in the axial direction relatively to the pressure plate 393, asub spring 397 for urging the pressure plate 393 in the clutchengagement direction through the sub pressure plate 310, a judder spring98 pinched between the clutch plate 94 and the pressure plate 393, and aspring holder 315 for receiving the main spring 395 and the sub spring397. The clutch center 392 and the pressure plate 393 are integrallyassembled with each other, and constitutes a clutch inner 390 disposedinside the clutch outer 91.

The lifter plate 396 is formed in a disc-shape, and disposed between theclutch center 392 and the lifter cam plate 84 (FIG. 3). The lifter plate396 has, at the center portion thereof, a bearing support hole portion396 a in which a ball bearing 87 is fitted.

The lifter plate 396 further has a release member 299 on a face thereofwhich confronts the clutch center 392. The release member 299corresponds to the release member 299 described with reference to thesecond embodiment, and it is fixed to the lifter plate 396 by a bolt211. The release bosses 271 of the release member 299 press the subpressure plate 310 by press faces 271 a at the tips of the releasebosses 271.

The clutch center 392 has a cylindrical hub portion 392 a fixed to themain shaft 56, and a disc-shaped receiving plate portion 392 a whichextends outwards in the radial direction from the axial end portion ofthe hub portion 392 a till a neighborhood of the inner peripheralsurface of the clutch outer 91. Through-holes 392 c through which therelease bosses 271 of the lifter plate 396 penetrate are formed in thereceiving plate portion 392 b. A plurality of through-holes 392 c areformed to be arranged in the peripheral direction of the hub portion 392a. Furthermore, the receiving plate portion 392 b has a reception face392 d for receiving the clutch plate 94 at an outer peripheral portionof the receiving plate portion 392 c which is located at the outside ofthe through holes 392 c.

The pressure plate 393 has an inner disc portion 393 a which is disposedto confront the receiving plate portion 392 b of the clutch center 392inside the clutch outer 91, an inner cylindrical portion 393 b whichextends from the peripheral edge portion of the inner disc portion 393 ato the disc portion 91 a side of the clutch outer 91 in a substantiallycoaxial positional relationship with the main shaft 56, and a pressplate portion 393 c which extends outwards in the radial direction fromthe tip portion of the inner disc portion 303 b till a neighborhood ofthe inner peripheral surface of the clutch outer 91. Each inner frictionplate 94 b is provided to the outer peripheral of the surface of theinner cylindrical portion 393 b. The pressure plate 393 is formed to berotatable relatively to the clutch center 392 by only a predeterminedrotational angle so that back torque is released.

A fitting hole 393 d which is freely slidably fitted to the outerperipheral surface of the hub portion 392 a of the clutch center 392 isformed at the center of the inner disc portion 393 a. A hole portion 393e in which the release bosses 271 of the release member 299 are insertedis provided around the fitting hole 393 d in the inner disc portion 393a. The flange ring 270 of the release bosses 271 is larger in diameterthan the hole portion 393 e in the radial direction of the releasebosses 271. A back torque limit member 312 which is in contact with thesubstantially whole surface of the inner disc portion 393 a isintegrally fixed to the pressure plate 393 inside the inner cylindricalportion 393 b.

FIG. 12 is a plan view showing the back torque limit member 312.

The back torque limit member 312 is formed in a disc-shape, and has, atthe center portion thereof, a hole 312 a in which the hub portion 392 apenetrates. A cam portion 101 b which penetrates through the inner discportion 393 a and a plurality of releasing hole portions 312 c throughwhich the release bosses 271 penetrate are provided around the hole 312a.

As shown in FIG. 11, the main spring 395 and the sub spring 397 arearranged at substantially equal positions in the radial direction of thepressure plate 393 in the space between the inner disc portion 393 a ofthe pressure plate 393 and the hub portion 392 a.

The main spring 395 is a coil spring extending in the axial direction ofthe pressure plate 393. A plurality of main springs are arranged to bespaced from one another at substantially equal intervals in theperipheral direction.

The sub spring 397 is a coil spring extending in the axial direction ofthe pressure plate 393, and disposed between the respective adjacentmain springs 395. That is, the main springs 395 and the sub springs 397are arranged to be out of phase with each other in the peripheraldirection of the pressure plate 393 inside the inner disc portion 393 a.

A ring-shaped clip 302 is inlaid in the outer peripheral surface of thehub portion 392 a, and the clip 302 supports a ring-shaped retainer 303.

FIG. 13 is a plan view showing the spring holder 315.

The spring holder 315 is formed in a disc-shape and disposed to confrontthe inner disc portion 393 a.

The spring holder 315 has a hole 315 a at the center thereof, and aplurality of cylindrical pocket portions 315 b, 315 c which areconfigured to have bottoms and provided around the hole 315 a and inwhich one ends of each main spring 395 and each sub spring 397 areaccommodated. The spring holder 315 is fitted to the hub portion 392 athrough the hole 315 a, and locked in the axial direction by theretainer 303.

Each main spring 395 and each sub spring 397 are fitted in the packetportions 315 b, 315 c, whereby they are positioned in the peripheraldirection.

Furthermore, the spring holder 315 has a plurality of projections 315 dprojecting outwards in the radial direction at the outer peripheralportion thereof. The projections 315 are fitted in groove portions 393 fformed on the inner periphery of the inner cylindrical portion 393 b,whereby the spring holder 315 is positioned in the peripheral direction.

At the peripheral edge portion of the hole 315 a of the spring holder315, a projection portion 315 e extending in the axial direction to theinner disc portion 393 a side is erected in the neighborhood of thepocket portion 315 c in which the sub spring 397 is accommodated.

FIG. 14 is a plan view showing the sub pressure plate 310.

As shown in FIGS. 11 and 14, the sub pressure plate 310 is disposedinside the inner cylindrical portion 393 b, and has a slidingcylindrical portion 310 a fitted to the outer peripheral surface of thehub portion 392 a, and a disc-shaped spring receiving portion 310 bextending outwards in the radial direction from the axial end of thesliding cylindrical portion 310 a.

The sub pressure plate 310 is movable in the axial direction along thehub portion 392 a. The projection portion 315 e of the spring holder 315is fitted in a groove portion 310 d formed on the inner peripheralportion of the sliding cylindrical portion 310 a, whereby the subpressure plate 310 is positioned in the peripheral direction.

The spring receiving portion 310 b is pressed by the other end of thesub spring 397, and brought into contact with the back torque limitmember 312. The press face 271 a of the release boss 271 inserted in thehole portion 393 e is brought, from the opposite side, into contact witha part of the spring receiving portion 310 b which is pressed by eachsub spring 397.

A cut-out portion 310 c which avoids the main spring 395 is formed at apart of the spring receiving portion 310 b which is overlapped with eachmain spring 395 in plan view, and the other end of the main spring 395passes through the cut-out portion 310 c and comes into contact with theback torque limit member 312.

The main spring 395 urges the pressure plate 393 through the back torquelimit member 312 to press the clutch plate 94 while the spring holder315 fixed to the hub portion 392 a serves a spring seat.

The sub spring 397 urges the pressure plate 393 through the sub pressureplate 310 and the back torque limit member 312 to press the clutch plate94 while the spring holder 315 serves as a spring seat.

That is, the urging direction of the sub spring 397 is identical to theurging direction of the main spring 395, which is the clutch engagementdirection.

Under the clutch engagement state shown in FIG. 11, the urging forcewith which the pressure plate 393 presses the clutch plate 94 is equalto the sum of the urging force of the main spring 395 and the urgingforce of the sub spring 397, and becomes the maximum value. The subpressure plate 310 constitutes a sub spring load transmission passage Sfor transmitting the urging force of the sub spring 397 to the pressureplate 393.

Under the clutch engagement state, the pressure plate 393 is pressed tothe clutch center 392 by the urging force of the main spring 395 and theurging force of the sub spring 397. Furthermore, under this state, thelifter plate 396 is pressed to the lifter cam plate 84 side through thesub pressure plate 310 and the release bosses 271 by the urging force ofthe sub spring 397, and a gap G is formed between the flange ring 270 ofthe release bosses 271 and the inner disc portion 393 a of the pressureplate 393. That is, under the clutch engagement state, the flange ring270 is separated from the inner disc portion 393 a, and located betweenthe inner disc portion 393 a and the receiving plate portion 392 b ofthe clutch center 392.

FIG. 15 is a cross-sectional diagram showing the clutch mechanism 351for gear shift under the intermediate-capacity state.

When the lifter cam plate 84 is moved in the clutch release direction inconnection with the rotation of the shift spindle 71 by the actuatormechanism 54, as shown in FIG. 15, the release bosses 271 of the lifterplate 396 are moved against the urging force of the sub spring 397, andthe spring receiving portion 310 b of the sub pressure plate 310 ispressed and lifted by the press face 271 a, so that the spring receivingportion 310 b separates from the back torque limit member 312 of thepressure plate 393.

The separation of the spring receiving portion 310 b from the backtorque limit member 312 cuts off the sub spring load transmissionpassage S, so that the urging force of the sub spring 397 is nottransmitted to the pressure plate 393 and thus the clutch capacity isdetermined by only the main spring 395. Therefore, as shown in FIG. 5,the clutch capacity decreases from the maximum capacity to theintermediate capacity instantaneously when the sub pressure plate 31separates from the back torque limit member 312. A first predeterminedlift amount L1 (first predetermined amount) of the lifter plate 396 atwhich the sub spring load transmission passage S is cut off may be setto be larger than zero, and it is determined by the dimensionalprecision of each part or the like.

The section from the separation of the sub pressure plate 310 from theback torque limit member 312 till the contact of the flange ring 270 ofthe release bosses 271 with the inner disc portion 393 a corresponds toan intermediate-capacity section. In this section, the sub pressureplate 310 merely moves relatively to the pressure plate 393, and has noeffect on the load of the main spring 395. Therefore, as shown in FIG.5, the clutch capacity is determined by only the main spring 395 in theintermediate-capacity section, and the intermediate capacity is fixed.

When the lifter plate 396 is moved by only the second predetermined liftamount (second predetermined amount) by the lifter cam plate 84 and theflange ring 270 comes into contact with the inner disc portion 393 a ofthe pressure plate 393 (not shown), the pressure plate 393 is pressed bythe flange ring 270, and moves against the urging force of the mainspring 395 and the sub spring 397 in the clutch release direction. Asmall-capacity section corresponds to the section from the contact ofthe flange ring 270 with the inner disc portion 393 a till the perfectrelease of the clutch.

When the pressure plate 393 moves and thus the press plate portion 393 cseparates from the outer friction plate 94 a 1, the clutch capacity isdetermined by the judder spring 98.

As described above, according to the third embodiment to which thepresent invention is applied, the hub portion 392 a of the clutch center392 is provided with the spring holder 315, and the sub spring 397, thesub pressure plate 310 and the main spring 395 are disposed between thespring holder 315 and the pressure plate 393, so that the main springd395 and the sub spring 397 can be compactly disposed at the same side.

The sub spring 397 and the main spring 395 are provided as coil springsalong the axial direction of the clutch mechanism 351 for gear shift tobe out of phase in the peripheral direction, and the sub pressure plate310 is provided with a cut-out portion 310 c through which the mainspring 395 is passed. Therefore, the spring characteristic of the coilsprings makes it easy to match the clutch capacity with a set value.Furthermore, the main spring 395 is passed through the cut-out portion310 c of the sub pressure plate 310, so that the sub pressure plate 310can be moved without affecting the main spring 395, and both thesecuring of the clutch load by the main spring 395 and the cut-offmechanism of the sub spring load transmission passage S are compatiblewith each other. A hole portion may be provided to the spring receivingportion 310 b in place of the cut-out portion 310 c, the main spring 395may be passed through this hole portion.

Fourth Embodiment

A fourth embodiment to which the present invention is applied will bedescribed with reference to FIGS. 19 to 24. In the fourth embodiment,the same constituent parts as the first embodiment are represented bythe same reference numerals, and the descriptions thereof are omitted.

The fourth embodiment is different from the first embodiment in that asub lifter plate 410 for urging the pressure plate 93 in the clutchengagement direction by a sub spring 411 which is provided in additionto the sub spring 97 is provided between a lifter plate 496 and thelifer cam plate 84, and the sub lifter plate 410 is lifted by apredetermined lift amount or more, whereby the urging force of the subspring 411 to the pressure plate 93 is cut off. In the fourthembodiment, the sub spring 97 is referred as a second sub spring 497 tobe discriminated from the sub spring 411.

FIG. 19 is a cross-sectional view showing a gear change mechanism 53, anactuator mechanism 54, a clutch mechanism 451 for gear shift and aclutch operation mechanism 52 according to the fourth embodiment.

The clutch mechanism 451 for gear shift has a lifter plate 496 forurging the pressure plate 93 in the clutch engagement direction by theurging force of the second sub spring 497. The clutch mechanism 451 forgear shift has a sub lifer plate 410 which is disposed between thelifter plate 496 and the lifter cam plate 84 (lifter cam) and pressed tothe lifter cam plate 84 to lift the lifter plate 496 in the clutchrelease direction, and a sub spring 411 which is provided between thesub lifter plate 410 and the clutch center 92 and urges the sub lifterplate 410 in the clutch engagement direction.

In the fourth embodiment, the clutch mechanism 451 for gear shift islonger in the axial direction by the amount corresponding to theprovision of the sub lifter plate 410, so that the cylindrical portion81 a of the clutch lever 81, the shift spindle 71, etc. are configuredto extend in the axial direction in connection with the increase inlength of the clutch mechanism 451 for gear shift.

FIG. 20 is across-sectional view showing the clutch mechanism 451 forgear shift.

The lifter plate 496 is formed in a disc-shape to be smaller in diameterthan the clutch center 92, and disposed between the clutch center 92 andthe lifter cam plate 84. The lifter plate 496 has a ring-shaped portion496 a, a spring pass hole 412 provided at the center of the ring-shapedportion 496 a, a sub lifter plate contact face 413 which confronts thesub lifter plate 410, and a pressure plate contact face 414 whichconfronts the clutch center 92 at the back side of the sub lifter platecontact face 413. The lifter plate 496 has a lifter plate side boss 415which projects from a neighborhood of the outer periphery of the sublifter plate contact face 413 to the lifter cam plate 84 side, and anannular sub spring receiving portion 416 provided on the whole peripheryof the outer peripheral portion of the pressure plate contact face 414.The sub spring receiving portion 416 is formed by inlaying the receivingmember 107 b into the step portion provided to the outer peripheralportion of the pressure contact face 414.

A plurality of lifter plate side bosses 415 are formed and arranged tobe spaced from one another at substantially equal intervals in theperipheral direction of the lifter plate 496. The lifter plate side boss415 is formed in a cylindrical shape, and has a hole portion 415 a inwhich the guide shaft portion 99 b of the release boss 99 (pressureplate side boss) is inserted (a hole in which the pressure plate sideboss is inserted), and an outer peripheral portion 415 b to which thesub lifter plate 410 is fitted. The diameter of the hole portion 415 ais set to be smaller than the outer diameter of the step portion 99 cand the outer diameter of the stopper plate 105, and also slightlylarger than the guide shaft portion 99 b so that the lifter plate sideboss 415 is slidable on the guide shaft portion 99 b.

The sub lifter plate 410 has a ring-shaped press plate portion 420(ring-shaped portion) which confronts the lifter plate 496, and acylindrical circular pipe portion 421 projecting from the innerperipheral edge of the center of the press plate portion 420 to thelifter cam plate 84 side. The press plate portion 420 is provided withthe circular pipe portion 421, so that the center portion which issubstantially coincident with the center of the main shaft 56 is opened.The main shaft 56 is a shaft for the clutch for supporting the clutchmechanism 451 at one end of the main shaft 56.

The press plate portion 420 has a hole portion 422 (a hole in which thelifter plate side boss penetrates) in which the lifter plate side boss415 of the lifter plate 496 is fitted. A plurality of hole portions 422are formed at the positions corresponding to the respective lifter plateside bosses 415. The hole portion 42 is formed to be slightly larger indiameter than the outer peripheral portion 415 a so that the press plateportion 420 is slidable on the outer peripheral portion 415 b of thelifter plate side boss 415.

A bearing support hole portion 424 to which the outer wheel of the ballbearing 87 is fitted is provided to the inner peripheral surface of thetip portion of the circular pipe portion 421, and the lifter cam plate84 is rotatable relatively to the sub lifter plate 410 through the ballbearing 87.

The circular pipe portion 421 has an annular spring receiving stepportion 423 which is provided on the inner peripheral portion 421 a soas to project inwards in the radial direction (a step portion extendinginwards in the radial direction). The bottom portion of the bearingsupport hole portion 424 is constructed by the spring receiving stepportion 423. The sub spring 411 is a coil spring provided coaxially withthe main shaft 56, and accommodated in the inner peripheral portion 421a of the circular pipe portion 421. The sub spring 411 is supported atone end thereof by the spring receiving step portion 423, and the otherend is passed through the spring pass hole 412 and supported by theclutch center 92. Specifically, the other end of the sub spring 411 issupported by the clutch center 92 through a step portion which isprovided to a washer 89 a interposed between a nut 89 and the clutchcenter 92.

The sub spring 411 urges the press plate portion 420 of the sub lifterplate 410 in such a direction that the press plate portion 420 isbrought into contact with the stopper plate 105 while the clutch center92 fixed to the main shaft 56 serves as a spring seat. The urging forceof the sub spring 411 is transmitted to the pressure plate 93 throughthe stopper plate 105 and the fixing bolt 106, and the pressure plate 93presses the clutch plate 94 as if it is pulled to the sub lifter plate410 side. That is, the urging direction of the sub spring 411 isidentical to the urging direction of the main spring 95, which is theclutch engagement direction.

The lifter plate 496 is provided to the release boss 99 while fitted tothe guide shaft portion 99 b, and the sub lifter plate 410 is fitted tothe lifter plate side boss 415 of the lifter plate 496. Thereafter, thetopper plate 105 (fixing member) and the fixing bolt 106 (fixing member)are fixed to the tip portion of the release boss 99, whereby the lifterplate 496 and the sub lifter plate 410 are assembled between the stepportion 99 c and the stopper plate 105.

The length in the axial direction of the lifter plate side boss 415 isset to be smaller than the interval between the step portion 99 c andthe stopper plate 105. Under the clutch engagement state shown in FIG.20, the lifter plate 496 is urged to the stopper plate 105 side by thesecond sub spring 497, and a gap G2 is formed between the step portion99 c and the pressure plate contact face 414. That is, under the clutchconnection state, the tip of the lifter plate side boss 415 presses thestopper plate 105 in the clutch engagement direction.

The plate thickness of the peripheral portion of the hole portion 422 ofthe sub lifter plate 410 is set to be smaller than the length in theaxial direction of the lifter plate side bosses 415, that is, theinterval between the stopper plate 105 and the sub lifter plate contactface 413. Under the clutch engagement state shown in FIG. 20, the sublifter plate 410 is urged to the stopper plate 105 side by the subspring 411, and a gap G1 (predetermined amount) is formed between thesub lifter plate contact face 413 and the press plate portion 420.

Under the clutch engagement state, the clutch plate 94 is pinched by theurging forces of the main spring 95, the second sub spring 497 and thesub spring 411, whereby the rotation of the clutch outer 91 rotated bythe primary gear 37 is allowed to be transmitted to the clutch center 92through the clutch plate 94 and the pressure plate 93, and the mainshaft 56 is rotated integrally with the clutch center 92.

When the pressure plate 93 is moved against the urging forces of themain spring 95, the second sub spring 497 and the sub spring 411 throughthe lifter cam plate 84, the pinch of the clutch plate 94 is releasedand thus the clutch is set to the release state.

FIG. 21 is an example of a diagram showing the clutch capacity of theclutch mechanism 451 for gear shift.

As shown in FIG. 21, in the fourth embodiment, the capacity of theclutch mechanism 45 for gear shift is made variable by changing a springwhich contributes to the clutch capacity. Specifically, the clutchcapacity is variable among plural stages of a maximum capacity C1 atwhich the clutch capacity is determined by the urging forces of the mainspring 95, the second sub spring 497 and the sub spring 411, a firstintermediate capacity C2 at which the clutch capacity is determined bythe urging forces of the main spring 95 and the second sub spring 497, asecond intermediate capacity C3 at which the clutch capacity isdetermined by only the urging force of the main spring 95, and a releasecapacity C4 at which the whole urging force of the main spring 95 isremoved.

The maximum capacity C1 of the clutch capacity is obtained under theclutch engagement state shown in FIG. 20. Under this state, both the sublifter plate 410 and the lifter plate 496 are in contact with thestopper plate 105 through the press plate portion 420 and the lifterplate side boss 415, and the urging forces of the sub spring 411 and thesecond sub spring 497 are transmitted to the pressure plate 93 throughthe stopper plate 105 and the fixing bolt 106. Therefore, the urgingforce with which the pressure plate 93 presses the clutch plate 94 isequal to the sum of the urging forces of the main spring 95, the secondsub spring 49 and the sub spring 411, and it becomes the maximum value.

That is, the lifter plate 496 and the stopper plate 105 constitute thesecond sub spring load transmission passage S2 for transmitting theurging force of the second sub spring 497 to the pressure plate 93.Furthermore, the sub lifter plate 410 and the stopper plate 105constitutes the sub spring load transmission passage S1 for transmittingthe urging force of the sub spring 411 to the pressure plate 93.

FIG. 22 is a cross-sectional view showing the clutch mechanism 451 forgear shift under the state of the first intermediate capacity C2.

When the lifter cam plate 84 is moved in the clutch release direction inconnection with the rotation of the shift spindle 71 by the actuatormechanism 54 (FIG. 3), as shown in FIG. 22, the sub lifter plate 410 islifted to the sub lifter plate contact face 413 side along the lifterplate side boss 415 against the urging force of the sub spring 411, andseparates from the stopper plate 105.

The sub lifter plate 410 separates from the stopper plate 105, wherebythe sub spring load transmission passage S1 is cut off, and the urgingforce of the sub spring 411 is not transmitted to the pressure plate 93,so that the clutch capacity is determined by the main spring 95 and thesecond sub spring 497. Therefore, the clutch capacity decreases from themaximum capacity C1 to the first intermediate capacity C2instantaneously when the sub lifter plate 410 separates from the stopperplate 105 as shown in FIG. 21. A first predetermined lift amount of thesub lifter plate 410 at which the sub spring load transmission passageS1 is cut off may be set to be larger than zero.

When the movement of the lifter cam plate 84 is continued after the sublifter plate 410 separates from the stopper plate 105, the sub lifterplate 410 continues to further move to the sub lifter plate contact face413 side so as to reduce the gap G1 (FIG. 20). The section from theseparation of the press plate portion 420 of the sub lifter plate 410from the stopper plate 105 till the contact of the press plate portion420 with the sub lifter plate contact face 413 corresponds to thesection of the first intermediate capacity C2. That is, the firstintermediate capacity C2 is obtained in the section of the lift amountof the lifter cam plate 84 which corresponds to the size of the gap G1.

In the section of the first intermediate capacity C2, the sub lifterplate 410 merely moves relatively to the sub lifter plate contact face413, and has no effect on the loads of the main spring 95 and the secondsub spring 497. Therefore, as shown in FIG. 21, in the section of thefirst intermediate capacity C2, the clutch capacity is determined by themain spring 95 and the second sub spring 497, and the first intermediatecapacity C2 is fixed. In the fourth embodiment, since a backlash basedon the gap G1 is provided, the section in which the first intermediatecapacity C2 is obtained can be lengthened, and the intermediate capacityof the clutch can be easily matched with a set value without providingany high-precision part and control method.

FIG. 23 is across-sectional view showing the clutch mechanism 451 forgear shift under the state of the second intermediate capacity C3.

When the lifter cam plate 84 is further lifted in the clutch releasedirection from the state of FIG. 22, the press plate portion 420 of thesub lifter plate 410 comes into contact with the sub lifter platecontact face 413, and the section of the first intermediate capacity C2is finished. Thereafter, when the lifter cam plate 84 further moves fromthe above state, as shown in FIG. 23, the lifter plate 496 is pressedthrough the sub lifter plate 410, lifted to the step portion 99 c sidealong the guide shaft portion 99 b against the urging force of thesecond sub spring 497 and separated from the stopper plate 105.

The tip of the lifter plate side boss 415 of the lifter plate 496separates from the stop plate 105, whereby the second sub spring loadtransmission passage S2 is cut off, and the urging force of the secondsub spring 497 is not transmitted to the pressure plate 93, so that theclutch capacity is determined by only the main spring 95. Therefore, asshown in FIG. 21, the clutch capacity decreases from the firstintermediate capacity C2 to the second intermediate capacity C3instantaneously when the lifter plate 496 separates from the stopperplate 105. A second predetermined lift amount of the lifter plate 496 atwhich the second sub spring load transmission passage S2 is cut off maybe set to be larger than zero.

When the movement of the lifter cam plate 84 is continued after thelifter plate 496 separates from the stopper plate 105, the lifter plate96 continues to further move to the step portion 99 c side so as toreduce the gap G2. The section from the separation of the lifter plate496 from the stopper plate 105 till the contact of the lifter plate 496with the step portion 99 c corresponds to the section of the secondintermediate capacity C3. That is, the second intermediate capacity C3is obtained in the section of the lift amount of the lifter cam plate 84which corresponds to the size of the gap G2.

In the section of the second intermediate capacity C3, the lifter plate496 merely moves relatively to the step portion 99 c, and has no effecton the load of the main spring 95. Therefore, as shown in FIG. 21, theclutch capacity is determined by only the main spring 95 and the secondintermediate capacity C3 is fixed in the section of the secondintermediate capacity C3. In the fourth embodiment, a backlash based onthe gap G2 is provided. Therefore, the section in which the secondintermediate capacity C3 is obtained can be lengthened, and theintermediate capacity of the clutch can be easily matched with a setvalue without providing any high-precision part and control method.

FIG. 24 is across-sectional view showing the clutch mechanism 451 forgear shift under the state of the release capacity C4.

When the lifter cam plate 84 is further lifted in the clutch releasedirection from the state shown in FIG. 23, the lifter plate 496 comesinto contact with the step portion 99 c, and the section of the secondintermediate capacity C3 is finished. Thereafter, when the lifter camplate 84 further moves from the above state in the clutch releasedirection, the pressure plate 93 is pressed through the sub lifter plate41 and the lifter plate 496 as shown in FIG. 24, whereby the pressureplate 93 moves in the clutch release direction, and the press plateportion 93 c of the pressure plate 93 separates from the outer frictionplates 94 a, whereby the clutch is released.

In the fourth embodiment, the judder spring 98 of the first embodimentis not provided.

As described above, according to the fourth embodiment to which thepresent invention is applied, the clutch mechanism 451 for gear shift isprovided with the main spring 95 for pressing the plural clutch plates94 in the clutch engagement direction between the clutch center 92 fixedin the axial direction and the pressure plate 93 displaceable in theaxial direction, the lifter plate 496 which is displaced by the liftercam plate 84 to lift the pressure plate 93 in the clutch releasedirection, the sub lifter plate 410 which is separate from the lifterplate 496, displaceable relatively to the lifter plate 496 and disposedto be nearer to the lifter cam plate 84 side than the lifter plate 496,the sub spring 411 which presses the pressure plate 93 in the clutchengaging direction through the sub lifter plate 410, and the sub lifterplate 410 is lifted by a predetermined amount, whereby the sub lifterplate 410 separates from the stopper plate 105 of the pressure plate 93and the sub spring load transmission passage S1 to the pressure plate 93is cut off. Accordingly, under the clutch engagement state, the load ofthe sub spring 411 which presses in the clutch engagement direction istransmitted to the pressure plate 93 through the sub lifter plate 410,and when the sub lifter plate 410 is lifted by a predetermined amount torelease the clutch, the sub spring load transmission passage S1 to thepressure plate 93 of the sub spring 411 is cut off. Therefore, theclutch engaging load can be secured by the main spring 95 and the subspring 411 which press in the clutch engagement direction, and undergear shift, the clutch engaging load can be produced by a load excludingthe urging force of the sub spring 411. Accordingly, the clutch capacitycan be set at multi-stages based on the maximum capacity C1 under theclutch engagement state and the first intermediate capacity C2 under thestate that the sub lifter plate 410 is lifted. Therefore, the clutchmechanism 451 for gear shift which can reduce shift shock by changingthe clutch capacity can be implemented with a simple construction.

The pressure plate 93 is provided with the guide shaft portion 99 bprojecting to the lifter plate 496 side, the lifer plate 496 is providedwith the lifter plate side boss 415 which projects to the sub lifterplate 410 side and has the hole portion 415 a through which the guideshaft portion 99 b penetrates, the sub lifter plate 410 is provided withthe hole portion 422 through which the lifter plate side boss 415penetrates, the stopper plate 105 and the fixing bolt 106 which are heldunder the state that the lifter plate side boss 415 and the sub lifterplate 410 are assembled are provided at the end portion of the guideshaft portion 99 b, and the load of the sub lifter plate 410 istransmitted to the stopper plate 105 and the fixing bolt 106. Therefore,the load of the sub lifter plate 410 can be transmitted to the pressureplate 93 through the stopper plate 105 and the fixing bolt 106, and thesub spring load transmission passage S1 can be formed with a simpleconstruction.

Furthermore, the length of the lifer plate side boss 415 is set to belonger than the length of the peripheral portion of the hole portion 422of the sub lifter plate 410, and when the sub lifter plate 410 is liftedby the gap G1 as the predetermined amount, the sub lifter plate 410 isbrought into contact with and displaced integrally with the lifter plate496. Therefore, the area of the first intermediate capacity C2 can beadjusted on the basis of the relationship of the lifter plate side boss415 and the thickness of the peripheral portion of the hole portion 422,and the lifter plate 496 can be directly lifted by the sub lifter plate410 after the sub lifter plate 410 is lifted by the gap G1.

Furthermore, the lifter plate 496 and the sub lifter plate 410 have thering-shaped portion 496 a and the press plate portion 420 which areconfigured as ring-shaped portions and opened at the center side of themain haft 56 of the clutch, and integrally provided with the circularpipe portion 421 which projects from the inner peripheral edge of thepress plate portion 420 to the lifter cam plate 84 side, the springreceiving step portion 423 extending inwards in the radial direction isprovided to the lifter cam plate 84 side of the inner peripheral surfaceof the circular pipe portion 421, and the sub spring 411 is disposedbetween the main shaft 56 and the circular pipe portion 421 in theradial direction and is in contact with the clutch center 92 and thespring receiving step portion 423. Therefore, the sub spring 411 can bedisposed compactly in the radial direction.

The second sub spring 497 for urging the pressure plate 93 in the clutchengagement direction through the lifter plate 496 is provided betweenthe clutch center 92 and the lifter plate 496, and the lifter plate 496is lifted by a predetermined amount or more, whereby the urging force ofthe second sub spring 497 to the pressure plate 93 is cut off.Therefore, the clutch engaging load can be obtained by the urging forceof the second sub spring 497, and also when the clutch is released, thenumber of stages of the clutch capacity can be further increased bycutting off the urging force of the second sub spring 497.

[Modification 1]

A modification 1 of the fourth embodiment to which the present inventionis applied will be described hereunder with reference to FIG. 25. Inthis modification 1, those parts which have the same constructions asthe fourth embodiment are represented by reference numerals, and thedescriptions thereof are omitted.

In this modification 1, the construction that the sub spring 411 asshown in the fourth embodiment is applied to the clutch mechanism forgear shift in which the sub spring and the sub pressure plate aredisposed between the clutch outer 91 and the pressure plate.

In this modification 1, only one lifter plate exists, and thus the sublifter plate 410 described with reference to the fourth embodiment willbe described while referred to as lifter plate 410.

FIG. 25 is across-sectional view showing the clutch mechanism 551 forgear shift according to the modification 1. The clutch mechanism 551 forgear shift has a clutch outer 91, a clutch center 592 which is providedinside the clutch outer 91 in the radial direction and integrally fixedto the main shaft 56, a pressure plate 593 movable in the axialdirection of the main shaft 56, a back torque limit member 512 providedinside the pressure plate 593, a clutch plate 94 provided between thepressure plate 593 and the clutch center 592, and a main spring 595 forurging the pressure plate 593 in the clutch engagement direction.

Furthermore, the clutch mechanism 551 for gear shift has a lifter plate410 for moving the pressure plate 593 in the clutch release direction, asub spring 411 for urging the lifter plate 410 in the clutch engagementdirection, a release member 599 provided between the lifter plate 410and the pressure plate 593, a sub pressure plate 510 which is providedinside the pressure plate 593 in the radial direction and movable in theaxial direction relatively to the pressure plate 593, and a second subspring 597 for urging the pressure plate 593 in the clutch engagementdirection through the sub pressure plate 510. The clutch center 592 andthe pressure plate 593 are assembled and integrated into one body, andconstitute a clutch inner 590 disposed inside the clutch outer 91.

The lifter plate 410 is formed to be substantially disc-shaped, anddisposed between the clutch center 592 and the lifter cam plate 84.

The release member 599 has a plate-shaped flange ring 570 which isformed to have a larger diameter than the hub portion 592 a of theclutch center 592, a cylindrical release boss 571 which projects in theaxial direction from the surface of the flange ring 570 to the lifterplate 410 side, and a cylindrical press boss portion 572 which projectsfrom the surface of the flange ring 570 in the opposite side to therelease boss 571. The press boss portion 572 is smaller in diameter thanthe release boss 571, and provided substantially coaxially with therelease boss 571. The release boss 571 is longer in the axial directionthan the press boss portion 572.

A plurality of release bosses 571 and a plurality of press boss portions572 are provided to be spaced from one another in the peripheraldirection of the flange ring 570 at substantially equal intervals. Athrough-hole 570 a through which a part of the back torque limit member512 penetrates is formed between the respective adjacent release bosses571 is formed in the flange ring 570.

The release boss 571 has a column portion 571 a penetrating through thepressure plate 593 and the clutch center 592, and a small-diameter bossportion 571 b which is formed at the tip portion of the lifter plate 410side thereof to be smaller in diameter than the column portion 571 a. Astep portion 571 c (a step portion of the release boss) having a largerdiameter than the small-diameter boss portion 571 b is formed at theboundary portion between the small-diameter boss portion 571 b and thecolumn portion 571 a. A stopper plate 505 constructed by a washer whichis larger in diameter than the small-diameter boss portion 571 b isprovided to the tip surface of the small-diameter boss portion 571 a,and the stopper plate 505 is fixed to the release boss 571 by a fixingbolt 506 which is screwed to the tip surface of the small-diameter bossportion 571 b.

The lifter plate 410 is fastened by the fixing bolt 506 while eachsmall-diameter boss portion 571 b is fitted in each hole portion 422(lifter plate side hole) of the press plate portion 420, whereby thelifter plate 410 is integrally connected to the release boss 571. Theinterval between the stopper plate 505 and the step portion 571 c is setto be larger than the plate thickness of the press plate portion 420,and the lifter plate 410 is movable in the axial direction along thesmall-diameter boss portion 571 b.

The clutch center 592 has a cylindrical hub portion 592 a fixed to themain shaft 56, and a disc-shaped receiving plate portion 592 b extendingoutwards in the radial direction from the shaft end portion of the hubportion 592 a till a neighborhood of the inner peripheral surface of theclutch outer 91. A through-hole 592 c through which the release boss 571and the tip portion of the pressure plate 593 penetrate is formed in thereceiving plate portion 592. A plurality of through-holes 592 c areformed to be arranged in the peripheral direction of the hub portion 592a. The receiving plate portion 592 b has a receiving face 592 d forreceiving the clutch plate 94 on the outer peripheral portion at theoutside of the through-hole 592 c.

The pressure plate 593 has an inner disc portion 593 a which is disposedto confront the receiving plate portion 592 b of the clutch center 592inside the clutch outer 91, an inner cylindrical portion 593 b whichextends from the peripheral edge portion of the inner disc portion 593 ato the disc portion 91 a side of the clutch outer 91 in a substantiallycoaxial positional relationship with the main shaft 56, and a pressplate portion 593 c which extends outwards in the radial direction fromthe tip portion of the inner cylindrical portion 593 b till aneighborhood of the inner peripheral surface of the clutch outer 91. Thepressure plate 593 is formed to be rotatable relatively to the clutchcenter 592 by only a predetermined rotational angle to release backtorque.

A fitting hole 593 d which is freely slidably fitted to the outerperipheral surface of the hub portion 592 a of the clutch center 592 isformed at the center of the inner disc portion 593 a. A hole portion 593e through which the release boss 571 is inserted is provided around thefitting hole 593 d in the inner disc portion 593 a. A plurality of holeportions 593 e are provided to be arranged in the peripheral directionof the inner disc portion 593 a. A ring-shaped hook member 530 isprovided to the inner periphery of the end portion of the innercylindrical portion 593 b. Each inner friction plate 94 b is provided tothe outer peripheral surface of the inner cylindrical portion 593 b.

A back torque limit member 512 is integrally fixed to the pressure plate593 inside the inner cylindrical portion 593 b of the pressure plate593. The back torque limit member 512 has a cylindrical portion 512 afitted to the inner peripheral surface of the inner cylindrical portion593 b, and a disc-shaped bottom plate portion 512 b which blocks thebottom portion of the cylindrical portion 512 a and confronts the flangering 570, and receives the main spring 595. A receiving groove portion512 d which is larger in diameter at the inner peripheral portion by onestage is formed at the tip portion of the cylindrical portion 512 a.

A plurality of boss through-holes 512 c through which the press bossportions 572 penetrate are formed in the disc-shaped bottom plateportion 512 b, and a cam portion 101 b penetrating through the innerdisc portion 593 a is provided to the disc-shaped bottom plate portion512 b. The cam portion 101 b is engaged with the lifter pin 120 fixed tothe clutch center 592. The cam portion 101 b has an engagement portion101 c which projects in the radial direction and engages with thepressure plate 593.

The engagement portion 101 c engages with the pressure plate 593, andthe end of the cylindrical portion 512 a is in contact with the hookmember 530, whereby the back torque limit member 512 is fixed to thepressure plate 593 in the axial direction.

A space 531 in which the flange ring 570 is accommodated is formedbetween the disc-shaped bottom plate portion 512 b of the back torquelimit member 512 and the inner disc portion 593 a of the pressure plate593.

The main spring 595 is a ring-shaped disc spring, and the outer diameterportion of the main spring 595 is supported by the receiving grooveportion 512 d of the back torque limit member 512 while the innerdiameter portion of the main spring 595 is supported by the retainer 103provided to the hub portion 592 a of the clutch center 592.

The main spring 595 urges the pressure plate 593 through the back torquelimit member 512 in a direction along which the clutch plate 94 ispinched by the pressure plate 593 and the clutch center 592, that is, inthe clutch engagement direction.

The sub pressure plate 510 has a sliding cylindrical portion 510 a whichis fitted to the inner diameter portion 512 e of the cylindrical portion512 a of the back torque limit member 512, and a disc-shaped bottomplate portion 510 b which blocks the bottom portion of the slidingcylindrical portion 510 a. The sub pressure plate 510 is movable in theaxial direction relatively to the pressure plate 593 inside the backtorque limit member 512. The bottom plate portion 510 b is urged by thesecond sub spring 597, and brought into contact with the disc-shapedbottom plate portion 512 b of the back torque limit member 512.

The second sub spring 597 is a ring-shaped disc spring provided betweenthe main spring 595 and the sub pressure plate 510. The outer diameterportion of the second sub spring 597 is supported by the bottom plateportion 510 b of the sub pressure plate 510, and the inner diameterthereof is supported by the ring-shaped retainer 503 provided to the hubportion 592 a of the clutch center 592.

The second sub spring 597 urges the pressure plate 593 through the subpressure plate 510 and the back torque limit member 512 while theretainer 503 serves as a spring seat, thereby pressing the clutch plate94.

That is, the urging direction of the second sub spring 597 is identicalto the urging direction of the main spring 595, and is the clutchengagement direction.

The release member 599 is disposed so that the release boss 571 isinserted in the hole portion 593 e of the pressure plate 593 and theflange ring 570 is located in the space 531. Furthermore, the press face572 a at the tip of the press boss portion 572 is inserted from thespace 531 side into the boss through-hole 512 c, and the press face 572a is in contact with the bottom portion 510 b of the sub pressure plate510. The size in the axial direction of the space 531 is larger than thethickness of the flange ring 570.

Under the clutch engagement state shown in FIG. 25, a gap G2 is formedbetween the flange ring 570 and the bottom plate portion 510 b of thesub pressure plate 510.

The lifter plate 410 is urged to the lifter cam plate 84 side by the subspring 411 interposed between the spring receiving step portion 423 andthe clutch center 592.

Under the clutch engagement state, the lifter plate 410 is urged by thesub spring 411 so that the press plate portion 420 is in contact withthe stopper plate 505, and the gap G1 is formed between the step portion571 c and the press plate portion 420. The urging force of the subspring 411 which is transmitted to the release member 599 through thestopper plate 505 is transmitted to the pressure plate 593 through theflange ring 570.

That is, under the clutch engagement state, the pressure plate 593 isurged in the clutch engagement direction in such a way as to be pulledby the sub spring 411.

The clutch mechanism 551 for gear shift has the same clutch capacity asthe clutch mechanism 451 for gear shift as shown in FIG. 21.

As shown in FIG. 21, in this modification 1, the clutch capacity isvariable at four stages of a maximum capacity C1 at which the clutchcapacity is determined by the urging forces of the main spring 595, thesecond sub spring 597 and the sub spring 411, a first intermediatecapacity C2 at which the clutch capacity is determined by the urgingforces of the main spring 595 and the second sub spring 597, a secondintermediate capacity C3 at which the clutch capacity is determined bythe urging force of only the main spring 595, and a release capacity C4excluding the whole urging force of the main spring 595.

The maximum capacity C1 of the clutch capacity is obtained under theclutch engagement state shown in FIG. 25. In this state, the subpressure plate 510 is in contact with the back torque limit member 512through the bottom plate portion 510 b, and the urging force of thesecond sub spring 597 is transmitted to the pressure plate 593.Furthermore, the lifter plate 410 is in contact with the stopper plate505 through the press plate portion 420, and the urging force of the subspring 411 is transmitted to the pressure plate 593 through the stopperplate 505, the fixing bolt 506 and the release member 599. Therefore,the urging force with which the pressure plate 593 presses the clutchplate 94 is equal to the sum of the urging forces of the main spring595, the second sub spring 597 and the sub spring 411, and becomes themaximum value.

That is, the sub pressure 510 and the back torque limit member 512constitute the second sub spring load transmission passage S2 fortransmitting the urging force of the second sub spring 597 to thepressure plate 593. Furthermore, the lifter plate 410 and the stopperplate 505 constitute the sub spring load transmission passage S1 fortransmitting the urging force of the sub spring 411 to the pressureplate 593.

Here, the operation of the clutch mechanism 551 for gear shift will bedescribed.

When the lifter cam plate 84 moves in the clutch release direction, thelifter plate 410 is lifted to the step portion 571 c against the urgingforce of the sub spring 411, and separated from the stopper plate 505.

The lifter plate 410 separates from the stopper plate 505, whereby thesub spring load transmission passage S1 is cut off and the urging forceof the sub spring 411 is not transmitted to the pressure plate 593, sothat the clutch capacity is determined by the main spring 595 and thesecond sub spring 597. Accordingly, the clutch capacity decreases fromthe maximum capacity C1 to the first intermediate capacity C2 as shownin FIG. 21 instantaneously when the lifter plate 410 separates from thestopper plate 505. A first predetermined lift amount of the lifter plate410 at which the sub spring load transmission passage S1 is cut off maybe equal to be larger than zero.

The first intermediate capacity C2 is obtained in the section from theseparation of the press plate portion 420 of the lifter plate 410 fromthe stopper plate 105 till the contact of the press plate portion 420with the step portion 571 c. That is, when the gap G1 is equal to zero,the section of the first intermediate capacity C2 is finished.

In the section of the first intermediate capacity C2, the lifter plate410 merely moves relatively to the step portion 571, and has no effecton the loads of the main spring 595 and the second sub spring 597.Therefore, the first intermediate capacity C2 is fixed as shown in FIG.21.

When the lifter plate 410 further moves in the clutch release directionafter the lifter plate 410 comes into contact with the step portion 571c and the section of the first intermediate capacity C2 is finished, thesub pressure plate 510 is pressed to the press face 572 a. Accordingly,the sub pressure plate 510 is moved against the urging force of thesecond sub spring 597, and the bottom plate portion 510 b of the subpressure plate 510 separates from the disc-shaped bottom plate portion512 b of the back torque limit member 512 in the axial direction, sothat the second sub spring load transmission passage S2 is cut off. As aresult, the clutch capacity is determined by only the main spring 595.Therefore, the clutch capacity decreases from the first intermediatecapacity C2 to the second intermediate capacity C3 as shown in FIG. 21instantaneously when the bottom plate portion 510 b separates from thedisc-shaped bottom plate portion 512 b. A second predetermined liftamount of the lifter plate 410 at which the second sub spring loadtransmission passage S2 is cut off may be set to be larger than zero.

The section from the separation of the bottom plate portion 510 b fromthe disc-shaped bottom plate portion 512 b till the contact of theflange ring 570 with the disc-shaped bottom plate portion 512 b is thesection of the second intermediate capacity C3. In the section of thesecond intermediate capacity C3, the clutch capacity is determined byonly the main spring 595, and the second intermediate capacity C3 isfixed.

When the lifter plate 410 further moves in the clutch release directionafter the second intermediate capacity C3 is finished and the gap G2 isequal to zero, the pressure plate 593 is directly pressed through theflange ring 570 and the back torque limit member 512, whereby thepressure plate 593 moves in the clutch release direction and the pressplate portion 593 c of the pressure plate 593 separates from the outerfriction plate 94 a, thereby releasing the clutch.

As described above, according to the modification 1 of the fourthembodiment to which the present invention is applied, the clutchmechanism 551 for gear shift has the main spring 595 which is providedbetween the clutch center 592 fixed in the axial direction and thepressure plate 593 displaceable in the axial direction and presses theclutch plate 94 in the clutch engagement direction, the lifter plate 410which is displaced by the lifter cam plate 84 to lift the pressure plate593 in the clutch release direction is provided, the release member 599is provided between the pressure plate 593 and the lifter cam plate 84,the release member 599 is provided with the release boss 571 projectingto the lifter plate 410 side, the end portion at the release plate 410side of the release boss 571 serves as a small-diameter boss portion 571b which is smaller in diameter than the diameter of the release boss 571at the pressure plate 593 side, the lifter plate 410 is provided withthe hole portion 422 through which the small-diameter boss portion 571 bpenetrates, the end portion of the small-diameter boss portion 571 b isprovided with the stopper plate 105 which is held while the lifter plate410 is assembled with the stopper plate 105, and the fixing bolt 106,the sub spring 411 which is provided between the clutch center 592 andthe lifter plate 410 and presses the pressure plate 593 in the clutchengagement direction through the stopper plate 105 and the fixing bolt106, and the lifter plate 410 is lifted by a predetermined amount to beseparated from the stopper plate 105, thereby cutting off the sub springload transmission passage S1 to the pressure plate 593. Accordingly,under the clutch engagement state, the load of the sub spring 411 forpressing in the clutch engagement direction is transmitted to thepressure plate 593 through the stopper plate 105, the fixing bolt 106and the release member 599, and when the lifter plate 410 is lifted bythe predetermined amount at the clutch release time, the sub spring loadtransmission passage S1 to the pressure plate 593 is cut off. Therefore,the clutch engaging loads of the main spring 595 and the sub spring 411which press in the clutch engaging direction can be secured, and theclutch engaging load can be produced by a load excluding the urgingforce of the sub spring 411. Accordingly, the clutch capacity can be setat plural stages among the maximum capacity C1 under the clutchengagement state and the first intermediate capacity C2 under the statethat the lifter plate 410 is lifted, and the clutch mechanism 551 forgear shift which can reduce the shift shock by changing the clutchcapacity can be implemented with a simple construction.

Furthermore, the small-diameter boss portion 571 b of the release member599 is configured to be longer in length than the thickness of theperipheral portion of the hole portion 422, and when the lifter plate410 is lifted by only the amount corresponding to the gap G1 as thepredetermined amount, the lifter plate 410 comes into contact with anddisplaces integrally with the step portion 571 c of the release boss571. Therefore, the area of the first intermediate capacity C2 of theclutch can be adjusted on the basis of the relationship of thesmall-diameter boss portion 571 b and the thickness of the peripheralportion of the hole portion 422, and after the lifter plate 410 islifted by the predetermined amount, the release boss 571 can be directlylifted by the lifter plate 410.

Furthermore, the lifter plate 410 has the ring-shaped press plateportion 420 which is opened at the center side of the main shaft 56 asthe shaft of the clutch and is integrally provided with the circularpipe portion 421 which projects from the inner peripheral edge of thepress plate portion 420 to the lifter cam plate 84 side, the springreceiving step portion 423 extending inwards in the radial direction isprovided at the lifter cam plate 84 of the inner peripheral surface ofthe circular pipe portion 421, and the sub spring 411 is disposedbetween the main shaft 56 and the circular pipe portion 421 in theradial direction and is in contact with the clutch center 592 and thespring receiving step portion 423. Therefore, the sub spring 411 can bedisposed compactly in the radial direction.

Furthermore, the sub pressure plate 510 which is separate from anddisplaceable relatively to the release member 599 and the pressure plate593 is provided, the second sub spring 597 for pressing the pressureplate 593 in the clutch engagement direction through the sub pressureplate 510 is provided, and when the lifter plate 410 is lifted by thepredetermined amount, the lifter plate 410 separates the sub pressureplate 510 from the pressure plate 593 through the release member 599,thereby cutting off the second sub spring load transmission passage S2to the pressure plate 593. Therefore, the clutch engaging load can beobtained by the urging force of the second sub spring 597, and when theclutch is released, the number of the stages of the clutch capacity canbe further increased by cutting off the urging force of the second subspring 597.

[Modification 2]

A modification 2 of the fourth embodiment to which the present inventionis applied will be described hereunder with reference to FIG. 26. In themodification 2, those parts which have the same constructions as thefourth embodiment are represented by the same reference numerals, andthe descriptions thereof are omitted.

In this modification 2, the structure can be made compact by utilizingthe space in the axial direction which is formed by providing thecircular pipe portion 421 to the sub lifter plate 410 in the fourthembodiment.

FIG. 26 is a cross-sectional view showing the peripheral portion of theclutch mechanism 451 for gear shift according to the modification 2.

The power unit 16 has the crankcase 30 c as a power unit case in which acrankshaft 23 is accommodated. In the crankcase 30 c, one end of thecrankshaft 23 at the crankcase cover 30 d side in the crankcase 30 c isprovided with a start clutch 24. The main shaft 56 is disposed inparallel to the crankshaft 23 behind the crankshaft 23, and the clutchmechanism 451 for gear shift is provided to one end of the main shaft56.

The clutch operating mechanism 52 is supported by the crankcase cover 30d, and connected to the sub lifter plate 410 at one end in the axialdirection of the clutch mechanism 451 for gear shift. Specifically, theclutch operating mechanism 52 is connected to the circular pipe portion421 of the sub lifter plate 410 through the lifter cam plate 84 and theball bearing 87. The outer diameter at the start clutch 24 side of thepress operation portion 84 b of the sub lifter plate 410 issubstantially equal to the outer diameter of the circular pipe portion421.

The clutch mechanism 451 for gear shift is disposed to be nearer to theinside of the crankcase 30 c than the start clutch 24 and adjacent tothe start clutch 24. Specifically, the clutch mechanism 451 for gearshift is disposed so that the circular pipe portion 421 of the sublifter plate 410 and the outer case 39 of the start clutch 24 arelocated within the same width in the axial direction, and the pressplate portion 420 of the sub lifter plate 410 and the outer case 39 areoverlapped with each other when viewed in the axial direction of themain shaft 56. Furthermore, the fixing bolt 106 and the bottom face 39 aof the outer case 39 confront each other, and a predetermined clearanceis provided therebetween.

As described above, according to the modification 2 of the fourthembodiment to which the present invention is applied, the clutchmechanism 451 for gear shift is accommodated in the crankcase 30 c, andthe start clutch 24 through which the rotation of the engine 21 is inputto the clutch is disposed within the same width in the axial directionas the circular pipe portion 421 of the sub lifter plate 410 in thecrankcase 30 c. Therefore, the start clutch 24 can be disposed byutilizing the space of the circular pipe portion 421, and the crankcase30 c can be miniaturized even in the construction that the sub spring411 is disposed while the circular pipe portion 421 is provided.

Furthermore, the construction of the modification 2 may be applied tothe construction of the modification 1 so that the clutch mechanism 551for gear shift according to the modification 1 is accommodated in thecrankcase 30 c, and the start clutch 24 through which the rotation ofthe engine 21 is input to the clutch is disposed with the same width inthe axial direction as the circular pipe portion 421 of the lifter plate41 in the crankcase 30 c.

DESCRIPTION OF REFERENCE NUMERALS

-   -   21 engine    -   24 start clutch    -   30 c crankcase (power unit case)    -   51, 251, 351, 451, 551 clutch mechanism for gear shift (multiple        plate clutch)    -   56 main shaft (main shaft, shaft of clutch)    -   84 lifter cam plate (lifter cam)    -   91 clutch outer    -   92, 292, 392, 492, 592 clutch center    -   92 a, 292 a, 392 a hub portion    -   93, 293, 393, 593 pressure plate    -   94 clutch plate    -   94 a outer friction plate    -   94 b inner friction plate    -   95, 295, 395, 595 main spring    -   96 lifter plate (sub pressure plate)    -   96 b hole portion (hole portion smaller in diameter than the        stopper plate)    -   97, 297, 397 sub spring    -   98 judder spring    -   99, 271 release boss    -   99 b guide shaft portion (pressure plate side boss)    -   99 c step portion    -   105 stopper plate (fixing member)    -   106 fixing bolt (fixing member)    -   210, 310 sub pressure plate    -   210 c seat portion    -   212 d groove portion (seat portion of main spring)    -   212 e inner diameter portion (inlay fitting hole)    -   270 flange ring (flange portion)    -   293 e, 393 e hole portion    -   296, 396 lifter plate    -   310 c cut-out portion    -   315 spring holder    -   410 sub lifter plate (lifter plate)    -   411 sub spring    -   415 lifter plate side boss    -   415 a hole portion (hole through which pressure plate side boss        penetrates)    -   420 press plate portion (ring-shaped portion)    -   421 circular pipe portion    -   422 hole portion (hole through which lifter plate side boss        penetrates, lifter plate side hole)    -   423 spring receiving step portion (step portion extending        inwards in the radial direction)    -   496 lifter plate    -   496 a ring-shaped portion    -   497 second sub spring    -   505 stopper plate (fixing member)    -   506 fixing bolt (fixing member)    -   510 sub pressure plate    -   571 release boss    -   571 b small-diameter boss portion    -   571 c step portion (step portion of release boss)    -   597 second sub spring    -   599 release member    -   L1 first predetermined amount (predetermined amount)    -   L2 second predetermined amount    -   G1 predetermined amount    -   S, S1 sub spring load transmission passage    -   S2 second sub spring load transmission passage

What is claimed is:
 1. A multiple plate clutch having a main spring thatis provided between a clutch center fixed in an axial direction and apressure plate displaceable in the axial direction and presses aplurality of clutch plates in a clutch engagement direction, and alifter plate for lifting the pressure plate in a clutch releasedirection, characterized in that a sub pressure plate which is separatefrom and displaceable relatively to the pressure plate is provided, asub spring for pressing the pressure plate in a clutch engagementdirection is provided, when the lifter plate is lifted by apredetermined amount, the lifter plate separates the sub pressure platefrom the pressure plate, thereby cutting off a sub spring loadtransmission passage to the pressure plate, the sub spring and the subpressure plate are disposed at the opposite side to the lifter platethrough the pressure plate, the pressure plate is provided with a holeportion, the lifter plate is provided with a release boss to be insertedin the hole portion, and when the lifter plate is lifted by thepredetermined amount or more, the release boss comes into contact withthe sub pressure plate, whereby the sub pressure plate is separated fromthe pressure plate.
 2. The multiple plate clutch according to claim 1,wherein a flange portion which is larger in diameter than the holeportion of the pressure plate is provided to an intermediate portion inthe axial direction of the release boss of the lifter plate, and whenthe lifter plate is lifted by only a second predetermined amount, theflange portion comes into contact with the pressure plate and directlymoves the pressure plate.
 3. The multiple plate clutch according toclaim 2, wherein the multiple plate clutch has a clutch outer disposedat an outside of the clutch center in a radial direction, wherein theplurality of clutch plates contain outer friction plates provided to theclutch outer and inner friction plates provided to the clutch center,the outer friction plates and the inner friction plates beingalternately arranged between the clutch center and the pressure plate,the sub spring and the sub pressure plate are disposed between a hubportion of the clutch center and the pressure plate, and the main springis disposed between hub portion of the clutch center and the pressureplate to be nearer to the clutch outer side than the sub spring.
 4. Themultiple plate clutch according to claim 3, wherein both of the subspring and the main spring are provided as ring-shaped disc springs, thesub pressure plate is inlaid in the pressure plate, a seat portion ofthe sub spring is provided at an outside thereof in the radialdirection, and the pressure plate is provided with a seat portion forthe main spring at an outside in the radial direction of an inlay holein which the sub pressure plate is fitted.
 5. The multiple plate clutchaccording to claim 2, wherein the multiple plate clutch has a clutchouter disposed at an outside in the radial direction of the clutchcenter, wherein the plurality of clutch plates contain outer frictionplates provided to the clutch outer and inner friction plates providedto the clutch center, the outer friction plates and the inner frictionplates being alternately arranged between the clutch center and thepressure plate, a spring holder is provided to a hub portion of theclutch center, and the sub spring, the sub pressure plate and the mainspring are disposed between the spring holder and the pressure plate. 6.The multiple plate clutch according to claim 5, wherein the sub springand the main spring are provided as coil springs along the axialdirection of the multiple plate clutch so as to be out of phase in aperipheral direction, and the sub pressure plate is provided with a holeportion or cut-out portion in which the main spring passes.
 7. Themultiple plate clutch according to claim 1, further characterized inthat a release member is provided between the pressure plate and thelifter plate, the release member is provided with a release bossprojecting to the lifter plate side, an end portion at the lifter plateside of the release boss is provided with a small-diameter boss portionwhose diameter is smaller than the diameter of the release boss at thepressure plate side, the lifter plate is provided with a lifter plateside hole in which the small-diameter boss portion penetrates, an endportion of the small-diameter boss portion is provided with a fixingmember by which the lifter plate is held while the lifter plate isassembled, a sub spring for pressing the pressure plate in the clutchengagement direction through the fixing member is provided between theclutch center and the lifter plate, and when the lifter plate is liftedby a predetermined amount, the lifter plate is separated from the fixingmember, whereby a sub spring load transmission passage to the pressureplate is cut off.
 8. The multiple plate clutch according to claim 7,wherein the small-diameter boss portion of the release member is set tobe longer in length than the thickness of a peripheral portion of thelifter plate side hole, and when the lifter plate is lifted by apredetermined amount, the lifter plate comes into contact with anddisplaces integrally with a step portion of the release boss.
 9. Themultiple plate clutch according to claim 7, wherein the lifter plate hasa ring-shaped portion which is opened at the center side of a shaft ofthe clutch, and integrally provided with a circular pipe portionprojecting from an inner peripheral edge of the ring-shaped portion tothe lifter cam side, a step portion extending inwards in the radialdirection is provided to the lifter cam side of an inner peripheralsurface of the circular pipe portion, and the sub spring is disposedbetween the shaft and the circular pipe portion and is in contact withthe clutch center and the step portion of the circular pipe portion. 10.The multiple plate clutch according to claim 9, wherein the multipleplate clutch is accommodated in a power unit case, and a start clutchthrough which rotation of an engine to the multiple plate clutch isinput is disposed within the same width in the axial direction as thecircular pipe portion in the power unit case.
 11. The multiple plateclutch according to claim 7, wherein a sub pressure plate which isseparate from and displaceable relatively to the release member and thepressure plate is provided, a second sub spring for pressing thepressure plate in the clutch engagement direction through the subpressure plate is provided, and when the lifter plate is lifted by apredetermined amount, the sub pressure plate is separated from thepressure plate through the release member, thereby cutting off a secondsub spring load transmission passage to the pressure plate.